
Each guild would have their own guild hall connected together with a flag stand in the center to gain moral, and there could be other places to run the flag to get an obelisk or a rez shrine etc.
In the battles, you could probably choose the guilds you will fight for no rewards, or you could have a random fight for some sort of reward.
A reward for a random battle could either be just for faction, drops,or something else.

These fights could probably be farmed for profit if you are up against easy guilds, so the guilds fighting each other should probably be even in strengh like in rated GvGs.