Speaking of Rivian I think that the company couldn't handle delivering power trains to all these car manufacturers. They are currently a small company so I think they are more than happy right now to deliver their technology for other hypercars. Btw I think Rivian is currently more than busy developing powertrains and electronics for Mclaren, Aston Martin, and Pininfarina plus Porsche owns 10% of Rivian so they might have been helping them out with their Taycan as well.