You're absolutely correct. I have a friend who works for a company that does nothing but launch franchise changes, and they've had a few monster scores. They do it in a few ways. One is by, as you mentioned, taking a pre-existing successful restaurant and using the name and some of the menu.

Some times they will simply develop concepts (often 4 or 5 at a time) start one of each, and see what sticks.

I've studied the restaurant industry quite a bit and can only think of a few chains that stumbled into it.