The device I have in mind would just be a passthru device with a box of tricks in the middle.
That's not possible. There is a standard PC floppy controller inside the floppy case and just like the PC floppy controller on the motherboard cannot handle Amiga disks, the USB floppy controller cannot, either. There is nothing you could put in between, it won't work.
You rather have to rip the floppy controller from the external floppy case and replace it by a catweasel. This might be possible but also rather expensive as it needs a complete new design (USB instead of PCI). And very small as it needs to fit into the floppy case.
Additionally, there are not even useful drivers for the PCI catweasel card, who should write drivers for the USB version ?
Bye,
Thomas
