My specific use case is adding virtual MIDI ports via virtualMIDI - what you’re suggesting may very well work for USB MIDI (though I’m not sure based on what I’ve read about how Windows handles MIDI ports) but virtualMIDI appears to create actual WDM devices without any sort of USB intermediary which JUCE’s Windows MIDI implementation seems to have trouble picking up without restarting the application while the mentioned apps’ “rescan” functions handle it fine.
In the meantime I’m also contacting the virtualMIDI author to see if he has any ideas.