Though player housing would be good for this, I was more thinking of ideas that they could sensibly implement in the first round of the game. That is usually a major feature. At least in the first round of the game I don't think that would be feasible.
On the other hand, rather than sit-able...
As requested by Grummz, below is a list of ideas from games with good RP communities. Put together by talking to a few players across multiple RP communities. (Though most have the old City of Heroes community in common.)
Please feel free to add to this list or discuss below.
Minimum...