Here's some more material on MGZ2. The first video shows how to get the ring in the wall described in the notes, the second was supposed to show how to get Knuckles' rings but there was
a hitch.
The linked image shows approximately where on the map the problem arose. It's an invisible wall on the roof of the building. In the linked test videos, which I threw together this afternoon, I was unable to bypass the wall. If there is indeed no way around it - whether by somehow slipping through it or preventing it from spawning outright - then the strategy for collecting the rings outlined in my notes won't work, it seems.
You might notice if you play around in the dirtyMGZ movie, that wall isn't there, unlike my most recent test run. Edit: And when I say it isn't there, I mean it is there, but in a different form as it's possible to spindash through it. I don't know why it's present sometimes, but not others; however, I did take a different route to reach it in the previous trial. Yet, in an alternate version of the current trial, when I tried replicating that route, the wall was still there. These are the kinds of things only true geniuses like MarzoJr or WST will understand.
Perhaps a full test route run is in order, meaning tracing the exact route (whatever hypothetical route you choose) from the beginning of MGZ2 (beginning from the end of a 'safe' MGZ1 file, one in which you collect all the rings according to your intended route there) up to and including the problem wall to see what happens. Who knows, maybe something, some variable, would change along the way to solve the problem. I don't have time to perform this test myself, unfortunately. Or maybe dying or entering a starpost at some point would fix it? That's all I can think of.
Good luck man.
Edit: Oh, by the way, I see you said there were 19 rings on Knuckles route which you were thinking of forgoing. I know exactly which ones you mean. You should be able to collect at least 12 of them - all but the final 7. I'm not quite positive about this, but I'm pretty sure... you'd just need to either camera glitch back out of Drill Mobile's room or, if possible, use Tails to glitch through the speed shoes monitor and into the wall and go from there. It might even possible to get back out by going left over the roof, from the small outdoor area between buildings.
Edit: Yeah, I'm positive - I just tested and you can camera glitch back out of Drill Mobile's room, as long as you entered it and opened the trapdoor above beforehand.