One option I've seen at another game site I play, is the ability to vote/eject a player out of a game. All the other players must agree and issue a '[EJECT] playername' command in the chat box. This works well there because Automove isn't possible in that game (Roborunner at http://www.eyeplaygames.com ).

I know this doesn't quite solve the problem of a league whereby a disappearing player pretty much ruins it, epsecially in team play. Just another option to consider.