Musk wants to replace oil-driven vehicles with electric ones. He started Tesla Motors to point the way, willing to share in order to spread the word.
What is the quickest and easiest and most profitable way to do this? Manufacture and sell various model Teslas? Or simply supply turn-key electromotive units to other manufacturers?
What if, say, Ford just made bodies and Tesla just made the power plants? Both would save billions specializing. Tesla would not have to set up numerous incredibly complex vehicle assembly plants and Ford could ditch motor and transmission plants, and of course solve all of their regulatory problems concerning mileage and pollutants. And, per Tesla's success, Ford could make safer vehicles that would more easily meet future regulations there as well.
Also factor in the relative ease of producing AWD variants, and incorporating traction, brake, yaw, etc. controls.
And a "Powered By Tesla" emblem would elevate the brand like nothing else.
The key, as I always nag about, is to also set up Tesla Electron Stations everywhere to profitably charge up all the electric drive vehicles using their technology. Ford buyers are hardly going to accept extension cords and 5-hour charges in random locations.
You could envision Ford also wanting a piece of the charging station business because they would continue to make a profit on their cars for as long as they are being driven!
If this all makes sense for Ford, then maybe others would also want to join in as well. This scenario would allow Tesla to specialize and to be more than competitive with rival suppliers in al respects.
This could make Tesla the most profitable company on earth and serve to electrify the most vehicles and other things in the shortest time at the lowest cost possible.
It would also be a better option for potential partners like Apple. Apple likely does not want to make cars and get involved in all that. But, I could see them wanting to invest in the battery side of things and of course the in-car electronics. No need to invest in fenders and lug nuts...
Tesla stock might just rise a teeny bit (!) and there would be capitalization than they would know what to do with and this could lead to some spectacular innovations and projects down the road.
I think making cars will at some point just weight Tesla down, but of course they should still make a few special cars to keep the brand name upscale and desirable.