Any sort of Guild property would be awesome, especially with all of the features you listed.

I hate bringing up other games but stuff like Castles in RO (which you gained by conquering them in War of Emperium vs other guilds) can really make PvP group play shine. Even something similair in PvE (say you and your LS need to conquer an instance which is in a castle and is really difficult) would be pretty awesome.