It's entirely possible a 4-door Mustang which was simply a mustang stretched to fit 4 more doors could work, but I'm somewhat pessimistic. If there really is a desire in Ford to do a new V8 RWD seda based on Mustang's platform, I'd prefer they went in more of an Interceptor direction. I dont mean just re-do the Interceptor, I mean combine cues from past Ford sedans inside and out with the current company design language (or use it to launch a new one). Done right, I think they could do a heck of a good Falcon/Torino/whatever and it would stand without needing the Mustang name to prop it up.