Why not just make it so people can only enter a match if:
a) there’s an odd number of players, or
b) there’s an even number of players a second player is entering the match with them for the other teams
Especially the case for low numbers, where 2 v 1 is impossible to win.
And for tournaments:
Make it so it doesn’t start until all spots are filled on each team. So many times I’ve tried and people won’t warp into the tournament, and because we are outmanned, we have little chance. There needs to be a way to still let someone new in if the original team isn’t complete.