I'd much rather you conspired with Midgetalien to make the mod Skinjack just described, because that's a dead cool idea. But thank you very much for offering.
I wouldn't be much help there, not so good with scripting.
Adul made an armorer's hammer that required gold in order to use it, his expertise here could prove valuable.
As for the misfire thing, one could easily make spells (which utilize the "Summon Time = Magicka" scripting or no) that carry negative effects, and insert them into the game. Could make them cheaper and easier to perform for lower level magic-users, so that they'll choose/be stuck with those for the time being.
I was mostly thinking about the lowbie summons. It's always annoyed me that summons last just long enough to linger after one fight, and inconveniently vanish just when the next one begins. I never remember to re-summon stuff in a timely fashion, so the "Oh you need me? See ya, ha-ha! *Poof*" thing is a bit of a menace while a skele-archer can still murder poor little me in a couple of shots
There's a scroll somewhere that lets you summon a Daedroth for 2 whole minutes, I loved using that. Dunmer have no resistance to poison, which is a Daedroth's main weapon, so they drop like flies against those things.
Which brings me to the point behind summoning being limited: a clever player can do some epic damage with what the vanilla game has to offer alone. When I got the Spear of Bitter Mercy, Scourge, a Messenger Scroll (that's the one that summons a Daedroth for 2 minutes) and had made an amulet that summons a Golden Saint for 20 seconds, on the Xbox mind you, Divayth Fyr didn't stand a chance. And I was Level 15.