After a lobby is over, ask the host if he wants to continue the current lobby. If so, he could just supply a map name, and start a new lobby. This would be an awesome feature when a game is super close, and the majority of players want to continue playing or essentially do a re-match.
How would it work?
When the game is over, wait 60-90 seconds. Right when it ends, ask the host if he wants to continue. If so, have him provide a map name to start up on (by typing it--this could be improved with a custom plugin). After a map is chosen (assumed no continued lobby if no response), it will change to that map and initialize the server for the next game. Whoever has not disconnected will automatically be put into the lobby as the same class and team they were on. You would need some way of making these players say they are going to continue playing, because some tend to go AFK instantly after the game ends--maybe !ready or !continue to confirm? AFK's could be kicked on map change. This would make it easier to keep friends together, keep people playing TF2C (hopefully minimizing the wait time for lobbies), and keep fun/positive experiences going.
Of course if you had to go, you could just leave within those 60-90 seconds. If it was a super successful lobby, hopefully you will require only a few people.
Other notes:
- Would be like you are actually creating a new lobby, would need a new Lobby ID (especially if you guys implement Lobby History)
- With a custom plugin, you could have the remaining players vote for a map if the host wanted to continue