Does userland driver software, which probably wants to make all sorts of weird syscalls to communicate with hardware, tend to actually work under Wine?
I'll second this. I bought some ridiculous behemoth of a Fujitsu scanner that could do 60ppm 20 years ago when it was manufactured and got it working under SANE in Linux. I reported a bug that they fixed to make it work (it didn't initially) I think because it had really old firmware they'd never seen before.
I have so far successfully: used eeprom programmers, flashed a multi of android software, interfaced with a PLC from under wine with no problems or workarounds whatsoever
People have done it with vmware ESXi and passthrough. But you can't do it with say, Virtualbox. So with Firewire, real OS on the metal is usually the answer.