Ariel and Caterham are hardly major manufacturers, with a board of directors and shareholders to answer to.
And again, they skirt US regulations by selling the engine and the car separately. I'm not sure more than a handful of customers would be willing to spend the time and money to have to buy an engine and install it in their million dollar supercar.
But making a Prototype car for the road has been done before. Witness Willy Koenig and the Koenig C62 - basically a road-going version of the Porsche 962.
https://pic.armedcats.net/p/ph/phoenixsac/2011/06/11/koenig126135db.jpg
Produced in 1991, it was the McLaren F1/Bugatti Veyron of its day with a top speed of 237 mph.
But if more than 10 were ever built, I'd eat my hair.