First of all, TTK, welcome to the forum. These are great people.
Second, concerning the Auto-Harmonist feature - I have not found this to be one of the strongest feautures of BIAB, particularly as it cannot work with audio but needs MIDI to function. That stated, I do find it helpful in its Re-Harmonist format when I want to change some chords somewhere and want substitutes suggested. However, there is a 'sister' programme developed by Microsoft, in conjunction with PG Music, called 'SongSmith'. The primary function of this software is to generate arrangements based on a monophonic audio input (such as the human voice). It works with all the PG styles you already have and is not expensive at around $20. It works.
Third, as to Melodyne, I have this (though I only use it for pitch correction). I originally got a hold of it when I wanted the facility to sing a melody line into my computer and have it turn the notes into MIDI (so that I could use the Auto-Harmonist feature in BIAB). It is an excellent programme, albeit very expensive). But Bob, why would you want to input a generated RT into Meldoyne and convert it into MIDI? Of course, you can do that but I don't see the point as the MIDI notes for the RT are a notation of what the RT is playing and has no control over it, If you change the MIDI notation for an RT you will NOT change the RT being played.