I dont know if there is a way to make it, but two gamemodes in one map could be very interesting.
Maybe a map where two teams play koth or pong in one room from the map and the other two teams play dm, elim or ctf at the rest of the map (they cant come into the room with the other gamemode, but they should see them playing).
The only important thing is, that the mappers dont mix the gamemodes...