In my experience these kinds of problems need to be dealt with firmly, with a minimum of collateral damage, but in a reactive way that tells the vandal that they can't in general win, in no uncertain terms.
Messing around with proxy blocks and filters and stuff- it's much too brittle, it's probably never going to work.
I think the easiest and most effective way to handle this GRAWP issue is just to temporarily increase the account age requirement for page moves to (say) 6 months on the wikipedia, and make any account less recent than that go through an admin.
If it puts him out of business he'll probably get bored and stop.
In a few weeks we could try reducing it again, and if he starts back up, raise it again promptly.
The point is, there is no way around that; he can't win. Even if he ages accounts we just raise the requirement, wait a while, and then lower it again. Rinse, lather, repeat. The point is to give them the idea that they're up against an implacable obstacle; which... they are.