Musical notation is an abstraction, and this is why we still listen to 400 year old music, because it was never ‘hard coded’. Even the first performance was an interpretation of the notation. It’s also universal and has been described as the only universal language (probably not true). Best example of this is to listen to Glenn Gould’s late recording “A State of Wonder”. It contains both the original Goldberg recording from when he was 20 or whatever, and a recent interpretation. They don’t even sound like the same person. It’s a wonderful illustration of the principle that louder and faster is not better, and the benefit of artistic maturity.
Anyhow, MIDI and expression maps aren’t the same as this. MIDI obviously was invented as an electronic way to encode musical performance data. Doesn’t even make sense some of the time - take velocity. Invented for keyboard instruments, but as a wind player that means nothing to me. And what does Velocity of 50 mean? It’s patch dependent for one thhing, legato patches ignore it (generally, there’s no rules here) but short patches (usually) pay attention to it. Unless it’s an organ patch I suppose. Or if it’s NotePerformer, which mixes all of the data up into an algorithm which does a good job of sounding like what you want.
And Expressions can be whatever you want too obviously. Name them Alpha, Beta, Gamma etc. and it means whatever you want it to mean and map to whatever you want, but doesn’t help the next person who might look at your map. Now you can use musical terms here, but that’s just a shorthand for the primary source, and it still maps to whatever (you could map a short to a long).
Just some thoughts since you asked. Rounding back to the opening point, write a piece in notation (using whatever you want, photo of chalk on a cave wall, paper/pencil or printed out from Dorico) and stick it in a drawer. Your kids will be able to take that music and play it. But a DAW project, well as you know it’s standard practice to print stems because even next year you likely won’t be able to open up that project, due to changing software, plugins, etc. And of course if you want to recreate it somebody would take those stems and translate them back to notation.
I’m a software engineer by trade so am hyper aware of abstraction levels and languages, the example is the same as in a abstract programming language (e.g. C++) versus an assembly language - the latter being a baked version of the former. Or it’s like in physics translating from a tensor Hilbert space to say polar coordinates. Blah blah blah, I talk too much but you get the idea