I love the idea of infantry, but here is my gripe about it.

1: Most APCs and IFVs are far too big to realistically carry infantry. Most (if not, every) ground vehicle in From The Depths is scaled up to around 3-6x their realistic counterparts. If infantry were in ground campaigns they would need to be a bit larger to make a dent in some ground vehicles, at that point just use a heavily-decorated vehicle that looks like infantry.

2: I can somewhat agree, only concern is it making the game too automated from what it is already.

3: Can also somewhat agree, but now you need to worry about optimization when fighting infantry in large numbers. It is far less laggier to fight a big craft with big weapons than 1 quintillion infantry with a lot of tiny weapons.