Now-a-days
MVE/MVU/MVX & Cacus Mapvotes all have this ability afaik.
You can set them up to *Only Load* Mutators relevant to the current game.
And you can setup a bunch of CustomGames all using different Mutators. Also note that you can also load a large majority of *Server Actors* into the Mutator chain as well.
Also these Mapvotes can allow for Custom ServerPackages to only load for these specific Gametypes.
Meaning that the Server won't send 50-Billion Downloads to the client to play a 5min round of CTF. If configgured correctly and with some thought ... Admins can send bulk NW3 Packages to Clients IF those Packages are required by the GameType in question.
www.ut-files.com (although outdated) has alot of Mutators/Maps/Mods and all other things UT related. Also see above posts for more
