You have two problems:
1. You have to offer McDonald’s a nice wad of money to use the name, even though you can’t use their suppliers
2. You have to find a substitute for the treff ingredients that goyim think taste as good.
3. You have to make a profit without charging customers more than the McDonald’s prices even though you are paying substantially extra for ingredients and closing on Shabbos and Pesach (losing roughly one-sixth of your business).
You’ll probably conclude that being a kosher equivalent of McDonalds makes more sense economically than trying to be an official McDonalds.