I feel that having the registration open 24/7, as mentioned above, would be a bit too much since it could crash the server--but, having it open more often, of course, would be wonderful!
Perhaps, to help revive FH, we could all chat a bit more often and be less shy, and meet more people in-game! Friends always give others a reason to be active.
A mass-species group would be nice, but in all honesty I feel it would have to be very interesting to stay active for a long time--also, in my honest opinion, it'd have to be at least semi-realistic as well with a fantastic, unique backstory. As I've noticed, though I could be wrong, semi-realistic roleplays are the most popular!
Otherwise, more of us would need to learn how to mod, to make the community more active--stuff like that often attracts new or old faces. Admittedly, I absolutely love mods of all kinds myself, hehe.