Retaining the SE's yoke and manually adjusting was a possibility I was prepared to face, yes.
Yes, the recess could be widened, but the Classic II has only one recess line. Fitting a caddy-loader and the floppy drive side-by-side would be an adventure, to say the least. In fact, I'm fairly sure it's not possible without taking enough plastic out of the case to make your point about structural strength completely irrelevant ;-)
The curved Classic and Classic II are not by any means bad machines, not counting the fact that the computer guts themselves are pretty restricted... I don't know how to explain it, I find them pretentious almost. As if they're just screaming at you "Look at me, look at me, I'm so pretty despite being computationally weak!" ... Or perhaps that's just the voices again.
Glad to have your thoughts, gentlemen. If you think of anything else, please feel free to continue the speculamatin'