Oh, and another thought. One user pointed this out already and I have similar idea.
Few years back we say the rise (and fall ) of PCI expanders that were used to connect PCIe-x1 signals to mining GPU cards.
What if you simply make a board taller and add USB3 connector exposing PCIe signals.
There are already PCIe hubs out there that split signals to 3 or 4 PCIe-x4 connectors (with x1 signals) for people that want to use it.
But also USB3 kables can be used to create custom PCIe boards for any use case you desire