There are a lot of discussions around balancing issues. As other already stated in other threads: all people who think, that their fire team is overpowered, are free to just play with 3, 2 or 1 player.
The problem yet: at least one would have to stand still in the corner - as the game just allows for 4 vs 1.
It indeed could be fun, if you could choose the number of players - on both sides…
Imagine a battle with 40 soldier vs 10 predators. Or, as you suggested, if you could play team vs team too. Maybe even without any predator. OK, then the game should be renamed to just hunting grounds, I see :)
I agree, that there is a big potential in these kind of thoughts (as I guess it would not be too hard to program). So, let’s see, what the future brings…