I've played a lot of RPG over the years but not a terribly large amount of games with Fate mechanics, and those I played didn't have the equivalent of the SU abilities, just handling those with aspects.

I'm fairly comfortable with the basics of social conflict and overcoming obstacles in Fate.

I can pretty quickly grasp the impact of SU abilities on combat, and would feel pretty comfortable that I could field a highly combat effective character (wizard or otherwise), if I spent most of my refresh on abilities that increased stress done, mitigated damage and boosted skill scores.   So naturally my first choice to play in DF was a support/investigative character

My expectation is that a character like this would spend most of his time in combat setting up his more brutally effective allies to succeed, adding aspects to the scene or maneuvers to the enemy that targeted something other than their athletics or might, and then either compelling them at key moments, or passing +2 tags on to ensure that 8 stress attack from the Were-Rhino charge landed.

In most game systems, support characters tend to be ignored compared to flashier threats, but need to be able to handle a bit of collateral damage (like zonewide evocations or burning buildings) and the occasional attempt to focus on them and use threat of their injury/death to skew the battle.  (in D20, it's the "I need to be able to survive one round of full attack, or a bad surprise round").  To some extent just having fate points and some consequence slots free helps quite a bit, but one of the liberating things about a support character is that you can spend resources (skills/refresh) on things other than surviving getting your head torn off.

The trick is to not be so fragile any doof with a bottle can take you out, or that an alpha strike where an enemy mistook you for somebody physically dangerous doesn't kill you outright.   I think the concession rules help, as does "take out != death" sometimes.  But that said, I looked over my character and was just uncomfortable not taking some raw physical combat ability.   (in a Submerged game, he's got fists of 4 and the footwork stunt..he can beat up an average thug, or fight several or go one round with a ghoul without being torn apart instantly, but he'd do much better to find another plan than punching the enemy most days).

Another character in our game was advised to get a little athletics for similar reasons  - she's mostly a social character but you don't  want an average blow from a weapons 2 punk to take you out.

For people who've played support characters....how much is enough?   What are some of the options, especially if your concept doesn't really include athletic or combat training or aptitude?   Is this even a significant consideration in DF?  (it might not be if a small investment doesn't help much in the physical arena beyond the basic mechanics)

Some I've come up with on my own....
1.  Raw athletics pretty high.  Nice if you can fit it in and justify.  Inh speed's bonus counts to the total, as would athletics of a much more reasonable level (say 1-2) and a defensive stunt that raises it a bit in common for you circumstances (like being unarmed/unarmored)
2.  stunt that subs what you're good at as a block vs physical (there's a conviction stunt in Your Story like that)
3.  Some combination of toughness skills to boost a low athletics/endurance score.
4.  for spellcasters, some way of getting passive defenses when you don't have an action to block (see Harry's trenchcoat+boosted athletics as he got deeper into the war...he started out as a wheezy wizard with no defenses if he didn't raise a block)
5.  Veil/Stealth and some kind of way to contribute in a combat that doesn't rely on becoming visible.

For me, the magic number in a "submerged" game was endurance Average (the third stress box matters) and a 4 skill vs most physical attacks.   For the other character, she's got Average end & athletic, inh speed and inh recovery.  She'll get hit more often but recover faster, seems about a wash for me.  She started with Mediocre athletic and was advised to raise it a bit.

What's your experience?  How much defense do you bother with on characters who aren't expected to be so flashy/obviously dangerous in combat that they aren't likely to be focus-fired for long?

In the dresdenverse there are a lot of powers keen on making sure "Free Will of Mortals" or "The Mortal Ability to Choose" is enforced. 

The in-game mechanical effect of first (killing), second (no transforming), fourth (no enthralling) are likely mechanically enforced by the Power that entities like angels, the Knights, etc serve, and the extra power is a form of sponsored push by the kinds of folks who power the Denarians, at least two of the vampire courts and ghouls.  The 5th is probably also linked to this, as necromancy (as opposed to ectomancy) seems to deal with actual souls of mortals, not just a "footprint" left behind by their life, or just their bodies.  Although some necromancy doesn't seem to fall afoul of this (purely animating dead bodies) this would indicate why it is NOT a violation to animate the body of something that never had a soul.

The other 3 laws don't strictly apply to mortals with souls, but seem to apply to everything.

The events in Cold Days would indicate that at least one extremely powerful group of entities is interested in enforcing the 7th law (don't even THINK about dealing with outsiders).  Blame the mechanical effects of that on....read the book.  The slippery slope aspects of it fall under the opposition.

I'm less clear on the 3rd (reading minds),  and 6th (time).  My guess is actually it's the White Council who is enforcing these, for reasons of their own, as the original Merlin clearly did muck with Time, and the Gatekeeper and Blackstaff are exceptions in various ways, plus all Wizards get a bit of prophecy as they age.   The slippery slope side may have roots more in just an addiction wizards tend to get to the behavior (invading privacy or trying to fix mistakes in time with more meddling).

The political side (Wardens show up etc) is much more legalistic, and usually the error is on the side of "caution" although there is clearly a procedure that includes a soulgaze to help determine if the person is too far gone to be saved.

If I was going to change the mechanical behavior (get a boost when being bad, at the cost of becoming closer to an NPC or actually becoming one) I'd want to be damn sure I knew what the reasons for the laws were in my universe, and the purpose they serve to the cosmology.  Above are my guesses, and it would inform whether or not a person had to take a lawbreaker power, or whether they'd get by with a consequence or aspect change on a borderline violation...or whether much to their surprise nothing happens aside from any remorse they might naturally have for such an act.

I tend to lean toward the earlier idea that you just skin SU powers with faith-based flavor.

For toughness powers, the catch is that it doesn't work against mortals using mundane effects, because free will. (a wizard zapping you with a spell doesn't satisfy the catch.  A wizard who sets the building you are in on fire won't satisfy the catch in the direct attack, but invoking the mundane "on fire" aspect of the building would.  A demon punching you doesn't satisfy the catch, a wizard punching you would, unless he's magically enhancing his punch somehow).

The character I had in mind was based on the prophet who wrestled an angel and won.  He'd be the emissary of  Uzziel ("Strength of God") and in addition to the usual righteous/holy touch stuff to satisfy catch of the faith-based baddies he had SU strength and SU toughness.  I used human form +1 bonus to simulate that he could only manifest this strength against supernatural opponents, or barriers (blocks/maneuvers) keeping him from such opponents.  There was some aspect support to keep the powers in line with the vision.  The toughness soaked supernatural strength and/or claws type abilities pretty well, in addition to various magical attacks, his holy powers and SU strength meant he could hurt nearly anything even if he didn't satisfy the catch, obviating the need for a power like those of the Sword.

You could do a fair bit of this with just plain stunts too..."+2 to athletics to dodge attacks from non-mortal, non-mundane sources".   Likewise "+1 to guns when shooting opponents with unnatural defenses (like toughness, inhuman speed, magical blocks)" covers quite a bit.

What I like about this approach is it's all about your choices, not the choices of the other guy.  I don't have to know if my enemy has SU speed to know what my bonuses are, I just know that I get to use my SU strength on that enemy in this scene.

Likewise you can skin a lot of offensive powers as faith based.  My white court virgin evangelist had the usual white court incite fear abilities/feed fear which he never used, but when he had his Holy Book (+1 artifact) handy, he could wave it and preach and do weaponized (weapon 4, range) fear effects on supernatural enemies.  (the holy book could also stop bullets heh...but only if it was in his shirt pocket.  He did Guide My Hand by flipping through it and reading the verse, then deciding what to do...or preaching from it if substituting a skill)

If I'm going to generate a new faith based power, it needs to do something fairly unique.  I'm a fan of Guide My Hand, for example, because it helps with fate point economy (the fate points you save showing up as needed are used for the conviction-based power at need), letting you spend fate points on cooler effects than just being where needed.     

Something along the lines of just happening to have the right resource to beat a catch "I was inspired to get a butane lighter at Walmart today" seems to fit the faith powers better than just brute force defeating all catches the way the Swords do (those are major artifacts - that ability should be uncommon).

Why no one thinks of the obvious solutions? Magic evolved again and changed its quirk. It doesn't hex anymore. You are the first wizard of this generation.

I actually like better the other approach.  You're so old your magic just sours milk, etc.  But the impression I got from the Dresdenverse (or at least Bob) is that magic changes for everybody, not just individuals, although there is also individual variation.  So this approach is a fairly major change for the entire universe, where a magus working with the existing restrictions to minimize the risk (actually understanding tech as it evolves via scholarship, being low conviction, being good at thaumaturgy that blocks hexes, using circles when major work must be done) uses the existing paradigm and, for me, would be more fun because you'd have the "how do you DO that" from other practitioners aspect, including the suspicion that you might not be mortal at all.

You all have the right idea but are doing it backward for the simplest solution of the wizard who wants to use the Internet.

The wizard with the wireless keyboard is INSIDE the circle
All the other tech is outside.

Solves most of the power issues.  The wireless keyboard is a bit more of a problem but that's cheaper than a computer system and you don't have as many ergonomic issues (you can position the monitor etc at the right height, wizard in chair in circle etc).

Of course the easier system is to put the wizard inside the circle and have a minion.  Teach a faerie that you summon how to work the computer, for example.  Or put yourself in a circle, then have your mortal buddy power up their smartphone.  The only reason Butters had to use the GPS in the circle was that all of Chicago was under a hex at the time.  Hell, given how Bob the Skull's been used in the past few books, Harry could have had Bob doing his internet searches for a decade, if he knew what the internet was.

A real technomancer is a bigger problem, but just because Harry's anti-hex ward was pathetic in the TV studio doesn't mean a competent wizard who lacks aspects such as "Not so Subtle but Still quick to anger" and instead has things like scholarship 5 and a "Bleeding Edge Technophile" aspects couldn't do better.  If hexing is tied at all to how familiar the tech is, you should be able to invoke appropriate aspects to prevent inadvertent hexing of your own tech, as long as you keep a fate point or two handy.   And your Block against Hexing via Thaumaturgy could be much, much higher than your actual ability to hex even deliberately.

If I did a technomancer, step 1 would be conviction = Average.  Base the character on thaumaturgy, maybe have some magic item slots used for combat boom (or power foci for evocation or hell, just take mental stress if you really need to bust out some boom).  Most of the time you're a low risk to hex anything anyway.  Add that to routine thaumaturgy to screen what you carry and what's near you and a good discipline score and you're good to go.