I don't truly agree with keeping the old design, but how about if they made split models of the old muscle cars. Say they took a 1971 Mustang Fastback, made a throwback version and a modernized version, they would appeal to their respective sides making everyone happy. My stance on the new muscle cars, I like them all due to my love of the unique. I do get fairly annoyed when people freak out about the new models, you can just go buy the older models.
"Damn you kids these days and your plastic cars! Get off my lawn!" Just kidding, but there are plenty of beautiful cars these days. For example, the McLaren P1 is gorgeous. The new Charger is fugly however, like most of the new "muscle" cars. No, that's not a camaro, that's a life sized hot wheels.
Which is what the Japanese companies do with some of their cars which is why many of their cars are downright heinous (some of their designs are nice). One could say the same about how European cars are designed, they take every car nice or not that they make and make them into hideous wagons. The outside the box thinking doesn't really work, look at the Nissan Juke, you don't see many of those driving around because most people, me included, don't like its outside the box design. Do I like it? Yes, it's good, but seriously show the Hellcat version. It looks 100% better than this already good design.
Especially that econobox one that bares the name Charger. The Foxbody better wears the Mustang name IMHO.