Ethernet Switch used for CCA to CCA comm without FPGA/Proc for MAC
It is not so clear what you are asking, but if I understand correctly you want to operate both paths without using the FPGA.

You need to ask yourself why is the FPGA anyway used for. Since it is not so clear from your description nor the block diagram, I suppose you use it to manage the LAN9303 switch and the PHY.

If that's all indeed, then you can apply the switch configurations you need during boot, by using an external EEPROM, as the datasheet describes.

You could also apply the required PHY configuration using its special GPIOs for this purpose.

So, all in all, since the LAN9303 is an Ethernet switch, theoretically no external CPU is required for the Ethernet functionality, unless you need to apply special configuration or change the default configuration during operation.