There's a similar system, actually. Check out the book on Chaos magic. It's a lot like what you described, where you pick the range, shape, targets, damage/effect, and save, and it lists a DC to cast each. It also has a table for determining the nonlethal damage given to the caster. It's a lot like what you've described, in terms of mechanics. You could just tweak the flavor.

Encylopedia Arcane: Chaos Magic is the book. It's by Mongoose publishing.