The use case for 10BASE-T1S isn't quite clear to me. I get that you can do multidrop ethernet, which would simplify things a lot; no need to add switches or daisy chain anymore. And it's also not too slow, and you only need two wires.

But are microcontrollers with ethernet common? How cheap are they? A MAC needs a lot of pins compared to CAN which will increase footprint. And to really take full advantage of ethernet, you need a good networking stack and a solid set of utilities and applications on top. So Linux is the way to go in that case. But then you need a big processor with external RAM, eMMC, PMIC, several layer board, and don't forget a couple of Linux weirdos (speaking as one) who can actually develop in that environment. A lot of embedded guys can understand CAN pretty easily; show them gRPC and their heads may explode.

So I guess the use case is: embedded system with a lot of Linux boards that don't need that much bandwidth? Does that accurately reflect the architecture of a modern car?