Jeez, this is absolutely fantastic. I'm not even going to attempt it, but if (many years from now) I feel like I could at least semi-reasonably play (limp through?) it I'd love to give it a go. Only time and effort will tell I suppose.
Your entire Wordpress post was really enjoyable to read, although I'd be lying if I didn't say that some of the contents went over the head of a total beginner like me. I do feel like I learned some things, though. Your parallels between the themes of AIR and the general vibe of the music added a lot of cool flavor, and your writing overall is brimming with passion. Seriously, great read.
As @BlackHayate02 said this piece really needs a proper recording since the MIDI can't do it justice. That said I'd recommend you upload at least the full length MIDI here in case people want to listen without having to create a Sheethost account. Because that MIDI is still damn impressive.
I eagerly await your other AIR transcriptions since it's probably my second favorite Key OST (and VN), and has the most consistently good tracks I believe. Think I'll check out your other transcription notes after I go scratch my piano playing itch.
Thank you for all your good work.
It'd be nice to see some of the other talented people here posting instrumental Key covers. I know we've got skilled people hiding 'round here.