I would like to be able to choose a godly faction for other kinds of bonuses as well... What if I pledge allegience to Grenth, Lyssa, Melandru or Dwayna? Since PvP only can't really change their faction, all PvE allegiences and pledges should be broken with great penalties incurred (If I pledge allegience to Grenth, and then pledge allegience to Dwayna, I will be punished by spending 2 hours in the Underworld, unable to map out. Not a good example, but you get the idea).
Each allegience could offer different kinds of rewards for different kinds of services. Nothing big, but just something to add to the atmosphere

Well, I think PvP just got a whole lot more popular!