I am sure that it can be done, but OS9 drivers were even considered black magic back in the day, and now there aren't many people who understand the usage and development end.
To do it on a seamless OS level like on OS X, I think you'd need to make a system extension which included an entire MIDI driver setup, like MIDI Manager, OMS, FreeMIDI, etc have. That's not trivial even for somebody who knows how (and I don't). I suspect that one could work around it more easily by making a sufficiently generic OMS USB MIDI driver tha itself appears more or less class-compliant. But then it would be a challenge to get it to "play nice" with OMS way of doing things, which is basically the opposite approach of custom setups, names, etc.