I can't help but be old fashioned here. I like Blocktopia the way it is. The thought of leaving the old ideals scares me a bit. We've all seen how successful the G-Mod server was. It was fun at first, but ended up kinda dying within a month or two. I'd agree we need to rekindle the Blocktopia spirit, but I'm not sure that making different game servers is the way to do it.
I've always viewed the big four (Build server, Lava survival, PVP, SMP) as being rather necessary.
Here's my suggestion.
Stick with the big four, and bring back TNT. TNT was a huge people magnet. Every time I turn around, we have someone in the lobby asking "where am tnt server? i heard about tnt server and am interest". In addition to this, we should advertise, to bring in a fresh crowd. Now mind you, I know nothing about advertising, or if we in fact are advertising. Remember that the main time for crowds is summer. I don't believe that Blocktopia is dead. I don't think we need to pull something as drastic as to make an almost entirely new everything. Yet. Maybe my idea is just a bit optimistic, but it's just my opinion.