If you haven't played X-COM: Enemy Unknown, you really should give it a try. It's similar to the game you're describing, though the story for your characters is

If you haven't played X-COM: Enemy Unknown, you really should give it a try. It's similar to the game you're describing, though the story for your characters is much less authored. I bought the extra skins DLC pack and rewarded each soldier with unique armour when they reached the rank of Major. It was great.