|Pyromancer by DismalFiction/ DeviantArt|
USR has the luxury of being a super easy game that anyone can pick up and play, but when it comes to something as complex as magic, there's no set way of dealing with it. In Halberd Fantasy Roleplaying there's a system of keywords that work nicely, but are still not as simple as I'd like them to be. This is why I suggest magic being directly tied to specialisms.
Balance is an obvious issue with this method of using magic as it's difficult to know how much of an effect a spell has. If I gave my Necromancer a raise dead specialism (natch) then how easy is it for her to cast that spell? I'd approach it like any other task resolution in USR, using the difficulty table to determine how big the effect is. For example:
Easy (2) - You can probably bring an insect back to life, as long as it hasn't been squashed.
Medium (4) - Dead small animals and fish can be raised at this level.
Hard (7) - Larger animals, such as dogs or sheep, can be raised
Very Hard (10) - Now you can raise a humanoid creature
Impossible (14+) - You're able to raise larger or magical beings from the dead. Careful now!
The same goes for any kind of magic, or superpowers or technowizardry.
In the interest of balance, I'd recommend making sure your magic users have a specific niche. Sorcerer is too broad (and boring) and could easily become overpowered, but a Pyromancer is much more specialised and you can theme your specialisms accordingly. Hell, mash-up some different niches and make a character like the Inferno Necronaut, a magic user who can travel between the world of the living and dead while having the ability to conjure fire. That's so metal!
Specialisms: Travel to the spirit plane (Wits), Conjure flames (Action), Knowledge of the dead (Wits)
To this end, I wouldn't even think about creating a stock sword-and-board 'warrior' character. Why would you when you could create an Apocalyptic Demi-Titan who can create landslides as well as bust someone up real good with a blade?
Rule of cool, guys.