I was thinking since the 4v1 idea is what the game is and won't be changing... why don't make the optional antag, a week event every month?
In each month you have a week where the antag mode can be optional, for the queue for antag, you can throw them to whatever squad that decided to play against one, and avoid that much calculation of matches since the group already want to put on a fight with antag.
And then you can use the data that you collect from these events for further updates.