I'm guessing you want to enforce this as a requirement and not an option, right? Otherwise, if it were optional, people could just challenge each other with the finisher stipulation in place.

I think enforcing unique finishers could be good, but I think there would be couple of potential problems:

-How would you deal with the one hit wonders who come in, take the finisher away, and then bounce two weeks later? I think it would be pretty messed up if a long term member loses something to someone who's two weeks into the fed and ends up flaking.

-Our roster section isn't organized that well, and would be difficult for new members to tell if something is taken or not.

-There are several people who I noticed have finishers in their standard ten moves list. So either adding the move to your standard list of moves could be a way around the "lose your finisher" thing, or it creates a situation where you have to bar certain moves from people's lists.