UHC in ccg? No... There is tons of servers for uhc..
Anyways, my most enjoyable uhc would be:
1 life: You die, you're out of the server untill new match is ready.
World limit: The whole world from Z=-1000 X=-1000. (Walls are out of bedrock.)
Time limit: Since only 1 life, there would be 90 mins of gameplay. Then the players will be in a DM. (If everyone is killed before DM then it's over too.)
Some stuff that should be banned: Ghasts don't drop tears.
I mean cmon, uhc is ultra hardscore, meaning that health is not regenerating, and only 1 life.