In my interpretation:
Sponsored Magic provides a set of rotes (which can be applied to Evothaum if that is also provided) unless the character also has Evocation (in which case that provides the Rotes, and the Sponsored Magic is just adding its available evocation effects to those available through Evocation).

Important Note (TM):  There is a distinct lack of consensus regarding the actual workings of 'Thaumaturgy with Evocation's speed and methods'.  Take all statements and advice regarding this subject as the poster's personal opinion only unless expressed as a direct quote from YS, preferably with page numbers to check for yourself.

For example: my personal interpretation of 'Evothaum', derived from the sidebar on page 288 of YS, places particular emphasis on certain phrases, including prominent ones such as "evocation's methods".  Essentially, all I allow Evothaum to accomplish is to add a non-standard 'element' to a character's available evocation effects.  That's it.  Everything still has to be phrased (mechanically) as an attack, block, maneuver, or counterspell, regardless of its narrative representation ('attack' with a summoned swarm of demon-wasps?  sounds nasty!).  I don't allow multiple aspects to be created with a single maneuver;  I don't allow durations not expressed in exchanges; I don't allow direct skill-replacement effects (note the 'direct'; invoke-for-effect is a powerful tool, but also one subject to additional case-by-case oversight);  etc..

Looking at the future is called 'thinking about possibilities'; don't look to far, or your brain might explode from trying to grasp all of the branching possibilities and what minute differences will/would bring them about

Travelling to (or changing) the future is called 'that thing that we all do without magic being involved'; using magic to speed this up is not meaningfully differentiated from simply putting yourself into stasis long enough for it to happen on its own

Looking at the past is called 'studying history'; alternatively, just create a powerful enough telescope (possibly with magic) and use it to look through a scrying portal some unfathomable distance away

Travelling to (or changing) the past, or pulling things to the present from either the past or the future, is called 'a really bad idea; stop that'
(pulling things from the future changes their relative past; pulling things from the past removes them from the past and thus changes it)

This is my take on the relevant Law

I would amend what Haru said by clarifying that maneuvers must be at least 3 shifts (for a fragile aspect, and 4 for a sticky aspect), and need to be stronger if the relevant defensive skill of the target is higher than that (shift value at least equal to defensive skill, minimum 3).

Taran, I think you missed the limitation clause on the types of consequences that can be affected when doing that costing.
You can't use this against a gunshot, sword-wound, etc.
I think that drops it solidly down to the -1 range.

If someone in your group has access to them (or you can get them at your local library) I'd suggest taking a look at the Dresden comic book / graphic novels.
They portray things much more accurately than the tv show while being drastically condensed as compared to the original novels.

That said, if you do want to go with some of the episodes, I suggest the one with the dragonfire.  It captured the whole 'the Council are jerks and the Wardens are even bigger jerks' feel pretty well.
Might want to throw in some incubi and/or hellions(sp?) for the 'lots of nasty not-humans in the world'.
Thief's hand for 'the dark powers are always willing to help'.

So, to summarize:
It bugs me that I can make an item with a default "frequency of use" and take a minor hit to its strength to drastically increase its frequency (thereby decreasing the "opportunity cost" of using the item), but if I want to lower its intended frequency of use (increasing the opportunity cost), I can't actually get anything for that.

I'm looking for something that can be useful on the same timescale as a Severe consequence. That is clearly a higher opportunity cost than enchanted items has in the rules, both as written and (I think) as intended. Maybe enchanted items is not the way to go, mechanically - that's just where I was when I got the idea.

I recommend an adaptation of the Limitation rebate power developed on these boards.
My mind isn't working as well as it should at the moment, but that's where I would start with something like this.

Unfortunately, its presence implies that powers without such a clause do not require approval, which runs rather contrary to some basic principles of the system (cooperative character creation, etc).