How would that apply to, say, a Werewolf though? Reduce any bonuses he gets from his Inhuman Speed and Inhuman Strength by the amount of the threshold?

Or require a discipline check against the threshold to change form - one or the other.  A shapeshifter that explicitly turned into a real, physical, ordinary wolf wouldn't have their physical abilities reduced at all, though.

There is precedent for a threshold only stripping away some powers though. From the same wiki article I referenced earlier, in regards to Ghost Story:

I don't agree with your interpretation here.  Yes, it makes it harder for the WCV to access those powers.  Does that mean those are the only powers limited?  No, just that they're the ones Dresden mentioned that time.

Varies a ton by type of dragon - I'd strongly suggest going with a lower-case-d dragon, though; they're still incredibly potent creatures, but a bit more approachable.

For example, a scion of an eastern style dragon might possess a Pearl of Wisdom that grants them flight & sponsored magic (with themes of water/healing/growth/storms & a sponsor-agenda of 'maintain balance & energy flow in the world') - and be otherwise entirely human.
Or such a character might have Channeling & Ritual: Water, Human Guise, Aquatic, Claws, and Inhuman Toughness & Recovery with a +3 catch, and use the traditional 'Pearl of Wisdom' as a focus item for their magic.

A western style dragon's scion would probably be more focused on physical prowess - and less capable of feats of personal shapeshifting.  For such a character it might work well to add an Item of Power that grants Human Guise (and perhaps Glamours) - something he acquired by cutting a deal with a fae, or a gift from an otherwise-distant draconic parent, or even a device custom-crafted for him by the party's wizard (assuming there is one).

For an Emissary, agenda is important; start by putting the dragon in as a major local power, and see who its allies and enemies would be - an old and well-established dragon is almost always going to land on the 'preserve the status quo' side of that chart.  An emissary of such a beast is likely to be tasked with whatever "minor" matters the dragon considers to be beneath its notice - which could range from negotiating with other local powers, to collecting tithes from the dragon's allies, to exterminating a nest of Black Court Vampires that's disrupting the feng-shui of the area by their presence.

Or you could go with the opposite spectrum, with a very young dragon that's chosen to empower a PC emissary because it saw something in that character it could use to secure its newly-claimed territory - perhaps the PC has a significant magical talent, or is the heir to some bloodline that allows them to wield a specific Item of Power that the dragon owns.  (Side-note on this one: a young dragon is probably a vanishingly rare creature in the modern world, and likely to attract significant attention from powers looking to groom it as an ally for later - or to eliminate it now while it's still weak.)

Edit: Oh, and don't forget the unusual - a dragon might well include a quetzalcoatl style creature, especially if your game is set after Changes.  I don't know enough of the right lore to be much help in figuring out powers for something like that, though.

If you want a world-class workspace, I'd actually make that (part of) an aspect, or perhaps a stunt: +3 lore when you have time* & opportunity to go home and research - excluding any actual spellcasting uses of lore.  (For spellcasting bonuses from having a really good workspace, see crafting & thaumaturgy focus items.)

The actual sanctum / library rules that get mentioned a time or two in the book should, however, be ignored - as Dragoonbuster said.

_____
* How much time is needed?  Well, that's a GM call; I'd expect at least a few hours.

I'd also add a note on research - it's very easy to justify almost any level of this that you want.

For example, consider the Gruffs.  They're faeries.  Faeries are vulnerable to iron; everyone knows that.  Clear +2 researchability, right?  Well... actually, no, they're a clear example of a +1 researchability, because it takes significant research (Harry had to go consult with Bob) to realize that they're faeries.  (And without that key insight, knowing that faeries are vulnerable to iron doesn't help you figure out what to use against these strange goat-people.)

It wouldn't be hard to propose some unusual type of fae that got a +0 researchability just because its mere existence was only known to a handful of specific people.

Alternatively, it's not hard to just say "Well, someone figured out my catch and published it on the paranet; thus, it's a +2 researchability regardless of what it might otherwise have been." - and then you've got a good seed for a first adventure, detailing how that particular problem came about.

getting temporary allowance to cast outside of the Sponsor's agenda is going to come with stings.

Strings, too, but - especially for hellfire - this seems like a pretty apt typo.

Agenda's an interesting one, and should ideally be tied into the game setting.  Expanding influence and recognition is a good basic one; any such entity might have a goal of getting itself on the Accords, for example, or of expanding the number of mortals who have made pacts with it.  What else such an entity might want needs a bit more information than just "Ghost in the Machine".

Perhaps it's the spirit of Security, with an agenda of hunting down hackers and keeping people Safe (even if they don't want to be, or even if safety impinges on US ideals of freedom...)

Perhaps it's more a spirit of secrets and cryptography that communicates via complex mathematical formulae and has an agenda of making information public - and a final goal of bringing the supernatural to the public attention.

Perhaps it's more of a literal ghost, with an agenda that matches up with the former goals of whatever human left such an imprint on the ether.

Work out a bit more of who and what it is, and the agenda should become more obvious.

I didn't realize that you're taken out if all your stress of a particular type was filled, as long as you still had consequences.

Not quite - the take out comes when you can't absorb a hit with stress.  So if all your physical stress is filled, you can keep going just fine - until the next hit that deals stress.  (A hit that lands exactly and deals no stress won't take you out.  A hit that would deal stress, but can be reduced to zero by taking consequences also won't take you out.)

Also note that I disagree with people on the questions of "concession" versus "take-out" - from my point of view there's nothing wrong with trying to negotiate a concession that starts with "Okay, there's this hit incoming that I'd need to take a moderate consequence to absorb.  I don't think this conflict is worth a moderate consequence.  Can I negotiate an alternative?"  Of course, the table needs to agree that any concession offered under such conditions is at least as bad for the character as a moderate consequence.  An actual take out where the player doesn't have any narrative control left only comes when the player doesn't have a choice anymore - which should be a vanishingly rare state of affairs.  I highly suggest talking with your GM & gaming group over this, though; some people on the forums seem to think that it's fair game for the GM to kill a character if the player opts not to use one of their consequences to stay in a fight - and if you get a GM that has that sort of attitude, well, better to know about it when your character isn't dead.

Hm... Actually, I'd probably treat this as an aspect invocation rather than a ritual.

Why?  Well, let's see here: if you take a target out, you get to narrate that take-out - and can easily narrate using your necromancy to hold them on the edge of life and death.  In this situation, there's no chance of a death curse at all, because it's your take-out result and you're not killing.

The other option where a death curse can come up is if they decide to pre-emptively die and throw a death curse; mechanically, I'd treat this as a concession, and negotiate it (and the outcome of the curse) as such.  And that's where you can offer up a fate point to invoke your aspect as a kemmlerite to change the available range of concessions.