So regarding the 'sign up for battle' list, then you need to also have faction leadership online. So I propose adding a tick box on the planetwars tab: "I am active". This way tabs can be kept on who is actively online for the faction, and who is just chatting or playing in lobster pots.
The tick should probably automatically untick itself and give a message somewhere on the lobby screen (where the planetwars box pops up?) after a certain amount of time, to prevent people from ticking the box and then walking away for hours (or from faction leaders currently embroiled in a 2 hour battle for a key planet from having to split their attention between sending people to fight and doing actual fighting).
With that plus the signup list we'd have a system where:
- Leadership is actively kept track of with the tick box
- If there are no leaders online, the system could fall back on allowing anyone to join anything, to prevent paralysis of the faction as a whole
- If there are leaders online, the faction is much more coordinated
- Games can be better balanced ('They're attacking us with singularity-level players, let's not send in our dwarves', or vice versa)
- Faction leaders are encouraged to give everyone a chance at leadership, because you want leaders online at all times, increasing investment/participation