About 30 years ago , we in India had just 3 car companies, Hindustan motors(makers of the Ambassador(Old 1957 Morris Oxford) Premier automobiles(Maker of the Fiat 1100 of the early 60'S) and Standard motors(makers of the Herald-Triumph herald in the UK)
Believe me, these three companies, knowing that they had a monopoly, let their quality control go to hell, in fact, there was NO quality control, mercifully, the last named, Standard motors dug its own grave in the mid 70's as the cars were so bad that no one would buy them, Fiats survived mainly because of the taxi market, and the Ambassador because the govt: bought from them exclusively.
So forget about the notion of having just one large car company, not a good idea at all! any monopoly is to be avoided at all costs.
During the hey days of the Model T Ford, Henry Ford was once asked by a customer if he could have his car in a different colour from the usual black, he replied" You can have the car in any colour as long as it is Black" !!