I'm currently experimenting with an exhaustion casting system for mages out of slots. Basically if you've run out of spell slots and cantrips won't cut it, you can make take on levels of exhaustion equal to the level of the spell you want to cast, following all relavent exhaustion rules after the casting. Including dying outright if you want to use a 6th level spell. So far it has been working wonderfully
The only problem I see with that, not saying it's bad or anything it's actually very cool, but the brutality of 5e's exhaustion would probably mean it'd be VERY rarely used. At least as a player I'd probably only use it if we're all gonna die or something. Now, if you wanna have it be that way, cool, no problem. If you want people to use it more often, however, maybe limiting it to half the level of the spell as exhaustion levels, rounded up probably, might work better. Or maybe using the new rules for exhaustion levels they are doing D&D
The most brutal thing you can do is let the wizard cast the spell and right as everybody is filling their plates, cast dispel magic and watch all the food vanish.. The hungry eyed looks of devastation on the patrons is what all chaotic creatures would do..
