I’d love to see a system such as that used in Jagged Alliance whereby the hiring cost for different soldiers varied based on the starting attributes, perks, and equipment of those soldiers.
One criticism often levelled at PP is that once you lose your A team soldiers that any replacements brought in will be a bunch of duffers, so what if instead there were A team replacements already out there and available to hire, but maybe just unaffordable at the beginning of the game?