Nope, 400 (what you said you are getting on Cyp's profile) is the max... little/no possible privileges possible to be given after 400.
Nope, no more warp setting AFAIK I don't see how a custom prefix was open to abuse though, obviously you couldn't use swear words etc, but surely that wouldn't have resulted in abuse. I could potentially see how setting a warp could cause more problems Eg. complaints of griefing etc, having to protect those warps, but essentially 400 donors get more free stuff (kits) and /invsee.