I'm sure they could implement POW's in a sanitized way, in the Total War games like Rome or Medieval 2 there are prisoners, you can release them after the battle or even ransom them.
So here maybe you could have a counter that fills up the more you fight with the thousands or hundreds of thousands of prisoners you have taken, specially after an encirclement, you can't do anything cruel to them, its just there for flavor and immersion maybe some other mechanic down the line.
As it stands now we are supposed to kill ALL of them, they abstract some of it through trickle back but still, other games had prisoners and even slaves and they were still rated for teens.