and actually I need the same kind of support for AUv3, which supports multiple midi ports also (in LogicPro, up to 8 ports). VSL has one AUv3 plugin already out supporting this.
For AUv3mfx, it would be necessary to create plugins that can sit in the mfx slot of LogicPro, listen to up to 8 midi ports and output on up to 8 ports down the signal chain to the next plugin… With LogicPro, for example, we can use the Scripter plugin and javascript and we can see the port of every midi event, in addition to channel. We can change the assignment of each event to which port we want, etc. From Scripter’s perspective, its still just one midiqueue that is access, but each event has a port attribute associated with it, which can be handled appropriately by the script.
So anyway, JUCE would need some way to discern that inside processBlock also. And of course we need to be able to do something with JUCE that will provide more input and output midi ports to the host the proper way.
I’m also reasonably sure right now that JUCE hosting is getting confused by VST3/AUv3 plugins that are trying to use more then one input midi port.
So JUCE needs some updating in this area in a number of ways… I’m too new to audio programming to know how I might tweak the modules myself, or else I would.