I understand you have an arena map server already. But it seems when ever I want to play some arena pwnage the server is always empty or there is not enough people there to bother joining. I think that bringing the two totally new arena maps (lumberyard and ravine) back to the server would be great.
I have talked with a lot of regulars on the valve maps no mods server (#1) and it seems the only reason people don't like the maps is because they don't like having to sit out and spec for a round because their team lost.
Personally I like these maps I don't mind sitting out from time to time its a nice change of pace for the game. Lets face it though TF2 players cant seem to sit still for 5 minutes.
If there is a way you could fix it so that it allows all players to play at once (16v16) then I think that people might be more inclined to like these maps. I know on 24 man servers some admins have found a way to trick the map into thinking the server is a 32 man server so that all 24 players can play at once. I am thinking something like this might be able to done for a 32 man server, maybe through your plugin?
Any way the auto-shuffle is a nice way to keep the teams from being too stacked so I would propose that after a team gets the 5 wins in a row and the team gets its 1 point that the teams would then get shuffled up.
This is just an idea that I have had brewing in my head for some time now and though I would see what you all thought.