This a genius formula. I'm making a game where the looney toons characters are going up against the post cereal company. BECAUSE THEY USE ARTIFICIAL SWEETENERS IN THEIR PRODUCTS!!! I'll stick my own original character in there somewhere so I can at least feel a little creative.
Try to come up with an idea that isn't a soapbox for your opinions with already existing franchise characters tacked onto it just so you don't have to go through the effort of making original characters/story on your own. Make something unique and original. Tolken didn't become a great author from writing books about how much he hated the people who created radio.