Level 2 is simpler and more mature, so it should be easier to specify, package and integrate.

It can follow the traditional OEM outsourcing route, where OEM has high-level models and gets suppliers to implement the details. e.g. I can find public information that Subaru use Veoneer cameras, Xilinx chipsets, but defines their own algorithms. I would speculate they have an outsourced company convert algorithms to FPGA netlists/embedded code. (On the other hand, I know other OEMs have a more complex mesh of joint ventures)