Turning to a completely different particular possibility of synergy, I think it would be fantastic if the world of Rapid Composer and the world of Melody Paths could be linked up.
Understanding chord progressions with the IFR exercise "Melody Paths"
Imagine if any progression inside RC could be converted (and/or exported) into a melody path chart by a simple button press.
Or, perhaps a separate app to do it rather than RC itself.
The point in my eyes is that RC already has a fantastic database of chords. A Melody Path chart is merely a columnar representation of any chord progression showing now the notes comprising each chord fall inside a single octave. IOW, half or more of the work has already been done. It's fundamentally just a matter of output formatting to bring it on home.
Whether as a formal collaboration between Music Developments and IFR, or not, or as something done inside Rapid Composer, or not, I think the musical education enhancement potential here is very high, and programmatically, the job could be considered to be low-hanging fruit!