In terms of kontakt alone, there are things you could do. There are not A-D ports as part of the midi spec. Kontakt has the ability to have up to 64 separate listening midi channels on its own set of 4 midi ports, but these ports are generally not exposed to DAW's. However, they are always there. I have in the past made some scripts which basically insert CC's in front of every note, and then once inside kontakt, use the CC to encode which of the 4 A-D ports to send the event to inside kontakt. that makes it possible to have one instrument slot in LogicPro hosting one instance of kontakt and one instance of your plugin (as AUmfx), and theoretically, with the right multi-script in kontakt could have numerous tracks hitting up to 64 separate parts in kontakt. This is definitely possible.
Note also that in logicPro this is a distinction between tracks and instruments. Most DAW's on bind track and instrument channel strip into one conceptual thing, and LogicPro attempts to create that kind of illusion, but really you have tracks, and then you have inst channel strips. SO in the case of Kontakt you can potentially have up to 127 separate tracks...all of which send their midi to a single instrument channel where you have your AUmfx and Kontakt hosted. Then in your plugin you would encode midi in such a way to direct to the 64 possible midi channels in kontakt...given that you also use a multi-script in kontakt to direct to the four ports A-D
in the case of VePro, there are similar advantages...you can have many tracks which basically feed to a single VePro plugin on a single inst channel...and that can be handing hundreds of midi channels in VePro...so that is going to be a good way for your customers to intonate a larger set of channels hosted in VePro.