Personally, I'd like DeLorean Motor Company back.
DMC exist, but they are working from the original design. They are based in or around Houston, and just started selling a Delorean EV. I'd love to see a modern effort out of them.
Plymouth, Mercury, Olds, Pontiac, and Duesenberg all make the short list. Problems: Olds was great when they had independent influence, in the age of badge engineering though it's position in GM would be crowding Chevy and Buick, and they are making mucho dinero; Pontiac faces a similar situation, though would benefit from a Firebird the rest of the line up would overlap Chevy, and because specialty brands don't make bank, Pontiac is gone again; Plymouth is actually both of those in one package as FCA has all bases covered; and Duesy has been lost to time despite that as far as I know it was on par with Rolls Royce for a time, though I know nothing.
With all that, Mercury remains, and I can live with that. Ford is the entry level and performance, and with Lincoln setting course for straight luxury (I hope I hope I hope), that leave FoMoCo with an opportunity to fill the gap and compete with Buick and Chrysler.
Was tempted to pick Mercury, because of my 1968 Cougar, but remembered exactly what they did to the Cougar. They turned it from a muscle car to just Mercury's counterpart to the Ford Thunderbird. And then its life ended as a front-wheel drive compact.
I get the hate directed at the Cougar Gen 2 on, but I can attest personally to the Gen 7 cars being able to hold their own. It was a T-Bird. OK, the Firebird was a Camaro, what's the issue here. A true midrange brand, with a classy-yet-agile flagship, could be very viable.
TL;DR-Mercury.