If I understand you correctly, you want to use USB to connect all the drives?
then have a look at his:
I am new to Chia - #10 by Fuzeguy?
Not sure why you would need a lot lot of pcie lanes on your farmer? how much TB are you going for?
I’m using a M-ATX lga1151 board with a i3-6100 to farm 360 TB
One SAS HBA + a few SAS expanders, gives me 32 drives on 8 pcie lanes