I won't be validating any applications. That's definitely not pursuant towards the powers I would think such a position entails. I'd never allow my assistant GM to allow character applications.

I see an assistant GM's role as whip. The assistant GM knows the plot, knows when the PC's are going on a divergent path and sets the path aright. The assistant plays critical NPC's and performs dice rolling on the behalf of those NPCs, taking some of the burden away from the GM. The character application is by far, the single most area where people can upset the balance of any given RPG, areas where there are background conflicts and particularly in the form of identifying munchkins that use rules exploits.