As I understood it the question was one of being able to play conductor parts independently while a midi file plays, preferably saved in panel memories so your pre-programmed favourite sets of voices could be selected in combination with any midi file.

The simplest solution would be one that requires no modification to the midi file, otherwise you have a lot of work in prospect changing all your midi files on an individual basis. So a universal solution would ideally require no tracks re-voicing, moving, or even preparing in any specific track/part order. Re-voicing to NX (which I have lost count of the number of times I've described and recommended) is desirable to improve the sound, provided suitably sympathatic sounds are chosen, but takes us no closer to a solution to the question.

The easiest solution is decoupling the conductor parts from the midi file and preventing the panel memories from changing anything in the midi file. Then you can add your preprogrammed conductor sounds to any midi file you choose, without affecting it, irrespective of the state of the midi file.