You could do a really crude approach where you actually format the "disk" using the Macintosh and simply record the output signal at a suitable resolution, it's still a digital signal and it's based around transitions.

Then on replay you simply playback the signal and loop it over and over to simulate the spinning disk.

So effectively you have a set of 80 x 2 "tracks" (literally) that you record in such a manner, and also remember to provide the index pulse to simulate the opto-electronic detection of the little hole in the disk.

When the mac wants to read a sector it has to wait till to reads the sector preamble and identifier. You have to then also detect when the mac wants to write to those sectors.

So if you remember how floppies work, the formatting lays down the sector identifiers and blanked sectors, then writing only changes the sector contents, not the identifiers.

For example an IBM formatted sector looks something like