Ford achieved the ore-to-assembly goal in 1927. General Motors become the highest volume automaker in the US starting in 1931. Ford's sold a ton of cars too though. My point is just that Ford did extreme vertical integration and were successful. But GM did things differently and that worked for them too.

Looks like some of this has been studied by Harvard Business School: https://www.hbs.edu/faculty/Pages/item.aspx?num=45289

Anyhow, you tout Tesla's deep work in batteries, motors and electronics (and let's not forget glass, doors, seats and other areas where Tesla has decided not to out-source). I can see where another company might be the GM to Tesla's Ford - finding success buying some of the right bits and pieces rather than spending an insane amount of money (re-)inventing them for themselves.