Odin: Yes, long-time kicking of deconners/griefers would be my favored solution as well :-) So far the only solution is to quickly vote-kick them, which still takes too long... And today some griefer just responded to the vote kick with "ok I'll be back in 2 minutes" and indeed he was back :-/
next_ghost: Designated Builder might help, but I also think this makes the team too vulnerable while voting... So an admin would be needed anyway. Also, I'm not sure if voting is really always good (think of the "lets kick the opposite team's pro player" vote calls which often pass because many people don't seem to think when voting :)
Also, DB doesn't help against people who kill base with grenades or lucy... So I think DB would be better than nothing, but won't really solve the whole problem.
Btw. I've also seen apparently experienced players deconning, maybe just to skip over the current map. I could "understand" griefers, but I don't really see how I could enjoy a map without fear of deconning when I've just maddened the whole team with my deconning...