Some sort of master midi track which allows you to control a parameter(s) for multiple nested midi / instruments tracks would be invaluable.
A use case - let’s say you have a complex ostinato created over 12 different midi channels feeding into various VSTs. Now you want to non-destructively add a velocity ramp to one section of this ostinato using the Velocity Shift parameter. Currently, you have to manually edit this parameter for every midi channel. What I propose is a VCA style fader for midi channels which would allow you to input the Velocity Shift data once and have it apply to all the midi channels grouped within that ‘fader’.
This kind of control would speed up midi-based composition a lot for those of us who deal with lots of midi tracks in one project.