This is a very good idea although both attempts in FFXI were Fail: The Adventurers "Bar" in Jueno and the "Rentable" Coffee House in Aht were always empty. You pretty much have to force peeps to go there and I have the winner (I think):

Put Repair NPCs in the Taverns.

Everyone will go there and if there are Card Games, Chocobo Racing, Buff Drinks & Food, Bar Fights (PvP Leves), etc.maybe people will stay awhile and socialize (or brawl).