Instead of "A Wizard Did It," how about if "Wizard*s*" did it? My idea is to have a dungeon with eight sections, all more or less equally accessible, that each get harder as you go deeper into them, so the party can choose how to go about things. Each section, of course, was designed by an archmage of each of the eight D&D schools.
So... brainstorming. What would the low, medium, and high-level challenges be for the level designed by the Abjurer, Diviner, Evoker, etc?
I started this same thread on RPG.net, true, but got few ideas there. One good thing that came out of that discussion, however, is to have each "tier" only open up once all eight of the lower tiers are cleared, or maybe 6/8 of them or something. So you can't go Illusionist Low --> Medium --> High, because you'll get killed. So there's a barrier that simply prevents the party from going into the Medium zone of *any* section of the dungeon until they've cleared enough of the Low zones.