What you’re missing is (1) that the approaches you’re thinking of are dramatically more labor for every song and (2) the approach I’m taking can be incrementally improved to do quite a lot.
On (1), knowing the tempo and transforming the measures requires a complete and correct score, including any tempo variability like fermata, as well as all the details of the arrangement. Questions like “how many bars do they vamp for that voiceover segment?” and “how do I notate the dubstep breakdown?” take a lot of care and time.
The simplified chart that I did took about three sittings. The extended version would be 5-6. That’s for a relatively simple tune. For a more complex arrangement like typical prog metal it would take forever, while my simplified version would continue to take about the same 2-3 sittings.
On (2), I agree that the I agree that the sync sloppiness is super disconcerting. It wouldn’t be hard to fix. I could also easily add all kinds of other objects that you click on in time with the original recording. Animated gifs, guitar tab, video of a conductor’s hands.
So this hack is about finding a really feasible method to annotate music.