How about a Guild Hall!

[Colino]

I'm not against the idea of PVP/PVE bonuses, but basing access to guilds off scores or achievements might just enforce elitism between shells and players. In the end it will likely be handful of shells with people who don't play much who have done just about everything in the game.

But so does any sort of other competition... I mean if that's your concern then don't have any PvP or any sort of competition at all!