There is a melee mod I quite like, can't remember the server, maybe ViA. Sudden death was melee only, and it had all players forced to the same class (random). Not that we play any maps that have sudden death/stalemate though, but if we did it is definitely a great laugh.
I did try to find a mod that made it melee only when under a certain amount of players (like 6). Melee is pretty fun on empty servers, shame that not everyone plays by the rules though.
How about party mod during the day (off-peak times) till the server fills?