I wonder what it would cost to just run a cable from the PDS out the back to a box and just have a couple PDS slots there for exapnsion. Didn't somebody have expansion boxes for SE30's back in the day? You could leave one for an accelerator and 2 for normal se30 PDS mounted sideways so the PCB would be small (like a PCI riser card).

You could even provide a bay for SCSI and a small PS.

I mean if its going to cost $100+ make it unique.