Changing Volume on a Single, Sustained Note- a Thought

I was thinking how it might be possible to change the volume on a single, sustained note (crescendo on, say, a held clarinet note over several measures) since it currently cannot be trivially done due to how MIDIs take note input. Each part of a note contains two portions- the initialization of the note, and the sustain of the note. The initialization is the part that plays over and over- the thing you'll mostly hear whenever you do a tremolo. This portion is fixed-length. The sustain portion is the actual note proper when held, and is what actually changes length depending on the note. This is all handled in the soundfont. I was thinking... is there a way to program a special "sustain" version of a note that is just the sustained part of the note, without the initialization portion? If so, it would be possible to simply break down a note that's supposed to change volume while held into a bunch of smaller notes of just the sustained portion, and have each one change volume progressively. This would also work for things like trills and tremolos on woodwinds or brass (currently it sounds like each note requires a new breath, hence why the bass flute cannot actually be heard when doing a trill); having each note be the sustained portion would make it sound much more fluid and correct. I'm not sure if this is possible, but it is just a thought on how it could be done. This obviously makes sense for more instruments than others (it would be silly on a piano or drum).