The whole forced de-lvl sounds more like a punishment for cheaters than a fun game design. I could see it as a funny round idea, levels are reversed for the round. SINGULAR ROUND. Not as a permanent thing though.

I like your idea, but here's a counter-proposal.

How about a rebirth system? Once hitting 18, having the choice to rebirth (restart) as a level 1 mage. You get to keep your spells, and gain a reward for rebirthing. (Say, 10 AP points, or a few potions?).

Each rebirth added on top of the others can gain more rewards. So if you rebirth once, you get a potion and a few AP. The next you get more. Like an increment system of AP and Potions.

All of this is purely examples, I doubt it'll be implimented.

Nice, but that system would end the need to create higher levels in the game. 18 would be the forever cap. It would also discourage new players as they could never catch up to older dedicated players.

You guys are way over thinking it. It's called prestige. You have the option at 18 to give it all up for a little bit of prestige. New sigils and orbs would be a great incentive. Ie call of duty