These spells could add a lot of flavor to spell casting, would have cool downs and cast times appropriate to their power. We'd retain the extremely customizable system from previous games for standard spell effects, but certain previously overpowered spells(invis, 100% chameleon, levitation) could be gained from these with reasonable limitations for balance along with new ones and at high levels really epic stuff.
Edit - By feats I guess I mean perks. But you get the idea.