I'm very interested, need some details please:

Watching the Photos and reading your post, I guess your offer is the following:

A PCIe Switch-USB PCIe Riser combo board

and

a Custom Motherboard based on some low-end SOC with 8x PCIe x16 slots and maybe a integrated PCIe switch.

What are the specifications from the Custom Motherboard I need to know before consider your product:

CPU/SOC: ?

Memory (RAM) on board or slots ?

Boot method: USB, DOM, Integrated DOM ?

Supported OS, is a custom-kernel OS provided (to deal the 8 GPU restriction)?

About the Switch-PCIe riser, more details about the card (actual PCIe lines in use, Supported OSs, etc).

may you shown us a video on a working setups please?

I could order 150-300 from either solution (before qualification test - Barebones Boards Only, not interested on the "Case").