I’ve seen requests for Midi Guitar to track down to 8 and 9 string guitar tunings below C1 so i thought that the best way to do this would be to run Midi Guitar 3 and Midi Bass 2 simultaneously, and have their respective tracking ranges set to cover only certain notes.
If Midi Bass 2 can be designed to track down to a low B0 or lower on a 5 string bass, you could set it to track from B0 to B1, and then have Midi Guitar 3 set to track from C1 to the highest note on the guitar.
The important thing would be for each plugin to reject notes outside the specified range by ginv out silence, instead of warbled or untrackable notes.
For instruments with polyphonic pickups, you could have an instance of either plugin for each string, with each instance set to trakc only a specific range. This would work really well.