Since the topic here is numbers and through association, gang banging, here's my suggestion for "something to try"...
Create a 4th team, or drop it to two teams. Can gang banging still occur? To some degree, perhaps, but I don't think this will ever completely go away no matter what happens.
The way the maps are setup, if 4 teams start off, each team basically has a quarter of the map with a central point here all 4 teams converge. Gang banging in general usually occurs on the back sides of a team's real estate. With 4 teams, one of those teams is not going to have a back side connection to one of the other teams. If 2 teams start ganging another, that 4th teams has no option but to attack one of the ganging teams, which in turn forces them to pay attention and thus breaks up the ganging of the original team.
It certainly could end up in a ganging situation depending on real estate layout, but that is true regardless of the number of teams in the game.
Personally I favor a 2 team setup. It would provide more even game play I think, but the potential is there for one side to be lop-sided. Implementation of the time delay as proposed by HT in this situation would be most effective in a 2 team situation I think.
Having 3 teams and trying to balance numbers via a dynamic time delay wouldn't really fix anyhting I don't think. It would be too difficult to tune the delay and difficult to figure out the correct balancing.
Anyway, just suggestions, and as mentioned, certainly something to try...and can always be changed if it doesn't work.