I like the idea, but there's some flaws with having it.
1. As mentioned multiple times before, the game as a whole would be run by clans and there would be no wiggle room for solo players to fit the equation.
2. It would cause a clear split in the community and Im not too sure what that'd mean for multiple aspects of the server.
3. I can't speak for the staff, but Ill make an assumption. A Deadman Mode server would probably call for more staff to run said server. Don't get me wrong, there's plenty of staff, they'll probably just nees MORE to run a Deadman Server.
Now this doesn't necessarily mean I disagree with your suggestion. It's just sort of wishy-washy. I think it'd be a fantastic annual or biannual event if anything, just not its own seperate entity.