I think you did a very good job at backing up my point. And with a lot more detail too.
You're right that there really is no true answer as to what it should look like and the best answer is probably a generic one. It's really just Fords version of a car with a long hood, short trunk, front engine, rear drive, two door, four seat, sporty or performance oriented coupe or convertible. That's it and it leaves everything wide open to interpretation. For GM it's the Camaro, Chrysler it's the Challenger and a large number of great looking European cars follow that formula as well. So... at some point it's bound to have some similar appearances to those other cars.
I don't necessarily think it should have to bear a strong resemblance (or any) to the outgoing car. From 93 to 94 the cars looked nothing like each other and from 04 to 05 they looked nothing like each other. Yet all of them generally sold well. In this case Ford did a good job of trying to carry over the overall general shape and proportions of the old car while not making it look like just an evolution of it. It is different and time will tell how well it does.
I think our society quite often tends to be stuck in the past and generally unwilling to move on from what it knows and is comfortable with. Anything outside of that is just wrong and unacceptable to people.