Share a many-channel USB sound card between several stereo computers?

Roughly the opposite of a USB hub, made possible by the application-specific details.

I have a digital audio mixer that, in addition to the analog I/O, also offers 18 channels each direction on USB 2.0 as a "digital patchbay" of sorts.

I want to connect several different computers to it without using the analog inputs, and give each computer its own unique stereo pair in each direction. Is there a device that can go between and make that happen?

Requirements are:

• 1 USB 2.0 host, to talk to the 18-channel sound card.
• 2 to 9 USB devices, as copies of the sound card that the host sees, but with 2 channels each instead of 18, and whatever other changes that that requires to the descriptors.
• Map/patch each USB device’s channels to its own set of USB host channels with no overlap.

I didn’t draw all 18 channels, but I think you get the idea. As drawn, there are 4 USB hosts, each controlling its own separate bus, none of which interact directly with each other. Just moving data from one bus to another.

Perhaps better from a functional standpoint than modifying a given set of descriptors, I could go into the mixer’s settings and set the sound card to 2-channel mode which is known to work, and then clone it, so that each computer thinks it’s connecting to the 2-channel mode of that card. Then set the mixer back to 18 channels on USB, while the go-between routes each odd-even pair to a different computer’s 1-2.

If it makes a difference, this 18-channel sound card only supports 32-bit integer, little-endian (as if endian-ness matters for a direct passthrough), at either 48kHz or 44.1kHz to match the entire mixer’s sample rate. The USB host doesn’t get to choose; it just is what it is, based on the mixer’s setting.

Does such a device exist?