Dodge Omni GLH, because you know Dodge did have a sense of humor at one time. Plus there's not enough turbocharged hatchbacks in the world.
The closest we'll get is the new Fiat 500T, I'm guessing. Well, unless Dodge is still thinking about doing the Hornet. Then, yeah, that'd be a true Omni successor.
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Since I've had Ford on my mind the past six months or so, there are two cars I'd like to have a rebirth:
1) Ford/Mercury Capri: With so much push going towards a small, lightweight, rear-drive coupe, Ford really should stick their toe into the water with a new Capri. Of course, it really fell by the wayside later in it's life, but the basic idea is there.
Use the 2014/15+ Mustang chassis as a basic starting point, possibly cut it down a bit. Utilize EcoBoost engines across the board, start with the 1.6 and top it out with the 2.0L as a top-trim "RS2000" variant. Make the six-speed manual option standard, finally offer a version of the PowerShift automatic with a fully manual paddle-shift option.
Thing is, I doubt Ford could make a financial case for it when the Mustang is already so affordable. And that is truly, truly unfortunate.
2) Ford Falcon Futura, Sprint: With the Mustang debut, the Falcon was rendered irrelevant shortly after it's debut in 1964. Even though they were exactly the same car underneath, it was the dramatic difference in style that had the Mustang winning out.
A Falcon could serve as a "grown up" Mustang, and if they were to offer as many variants as there were for it's predecessor, it could significantly add to the markets with which the brand competes in. Personally, I'd stick to a coupe, sedan and wagon variant. Go toe-to-toe with BMW, make it a "poor man's 3-series," and sell a kajillion. Maybe. Make it a model that is only available with EcoBoost engines, don't offer a V8, and it might be a halfway decent idea. But, the existence of the Mustang is what kills it.
All of it would depend on Chevrolet getting the SS Sedan out the door, and the possible commitment to the Code eventually happening.