external control of fadein/fadeout in midi notes

[Perfect Human Interface]

ASR envelope is within VSTi if I understand, thus - may not work as expected.

Are you trying it say it wouldn't work because it's an effect plugin and not an instrument plugin? Envelopes will work in an effect plugin. I even made a synth that's loaded as an effect.

The only odd thing about you looking to do this type of thing "per note" is that that generally implies polyphony, or in other words it would still work with more than one note playing at once, and process independently for each note, simultaneously. If you're looking to control a single thing this way, outside of poly stream, that's impossible of course because there's only one of that target thing.

Now on the other hand, if you're looking to control something, triggered via MIDI, but it only needs to work "monophonically," i.e. it would either retrigger with a new note-on or it would ignore new note-on's until the first note sends a note-off, that's quite simple. Actually you can do that with poly just as well, just with voices limited to one.

Either way you can simply use MIDI to Poly and then wire your poly to an envelope, which will allow to to control a target value via that envelope, triggered every time you play a note.