4. Integrate NTOSKRNL.EXE into wine, add USB infrastructure to
NTOSKRNL.EXE so that kernel-mode drivers can access USB (probably
through libusb), and modify ntdll to forward the appropriate reads,
writes, and i/o control requests to NTOSKRNL.EXE so that the .SYS file
can handle them. This is the only way that works with .SYS files
out-of-the-box, the others all require a rewrite of the .SYS driver's
functionality. Architecturally, this is the best way, you wouldn't
need to change any code in wine to add a new driver.

Way 4 is probably the best and I hope it works at some stage, but it's
still a long way off seeing as how NTOSKRNL.EXE itself still isn't in
wine.

Correct me if I'm wrong, but you're saying that this approach would enable wine to work with (almost?) any USB device, which has a vendor specific, kernel-mode driver, using the vendor's supplied driver out-of-the-box. Sounds like the best approach to me too.

Maybe there are other people out there with the same problem as me, (or simply a desire to get better USB support in to wine) who would be interested in working on this too?

Jono