Replace MAC block with SGMII

Your L2 Switch will probably have an SGMII Interface so will still need an SGMII interface and MAC on your FPGA.

To all intensive purposes the L2 switch would look like a PHY to the FPGA MAC.

I believe the TSE is the way to go, put an SGMII interface out of your FPGA and connect to the L2 switch SGMII (Which will need to be configured in PHY mode NOT MAC Mode as SGMII is not symmetrical).

This would give you n ports of 10/100/1000 depending on what your switch provides