The appeal of Minecraft is never perpetual, unfortunately. I suppose mods and such could prolong the life of such a server.
I've had a crack at UHC a couple of times myself. I play too recklessly (in ALL games, not just Minecraft), so I'm not very good. Not that I didn't enjoy it!
I also took a look at the Build To Win mod, seems like it could be bunch of fun. Hasn't yet been updated to the most recent Minecraft yet, though...? So I haven't tried it yet.
I think a big issue will be organisation. Yes, there'd be a server there, but then there'd have to be times scheduled for events that cater for global timezones. Also a way to see exactly what mods (if any) are currently running.
What's the cost of a decent MC server?