Unfortunately, I too was not able to find any off the shelf solution that would address this set of requirements (or even just the USB 3.0 requirement). You are looking at the development of a custom M.2 card that provides these capabilities -- and, as was discussed with you previously, this card will need to do so within the limitation of no support for PCIe bifurcation.
The Gen7 NUC has thunderbolt.
Thunderbolt to USB3 is a pretty normal offering, do you now if the connector would then actually use the bandwidth from the Thunderbolt, or would the data be re-routed to the existing USB3 controller?
Thunderbolt to PCI, too, though the form-factor of those boards are preventive for us.
Thunderbolt to 4xPCIe mini would have been bullseye...