I doubt Tesla will sell to them, Elon has said a few times their vehicle output is constrained by how many battery cells they can make. If they sell those cells to other manufacturers, they won't be able to make so many cars themselves.

Making vehicles is hard. There are a lot of logistical and technological challenges, plus the deep penetration of cars into society means that marketing, perception, and utility are on the lips of the hyper-rich down to the common man.

With batteries... you just make batteries. With cars you have to score adequate or better in lots of different areas to be competitive.