Little late here but I'll give this a go. I think the best bet for a long running, community driven server would be Tekkit, as previously discussed. The only problem would be to drive interest and keep the energy levels high constantly around the server. With Tekkit, once you get to that highest level it does become mundane, as is the case with any vanilla survival world. I think this is why the server would need an ulterior motive, or something that can be a constant for players to strive for. Replay-ability is key here. Look to the recently added time trial system in zero for proof.