To make a Mac clone with an SD card floppy replacement, I don't think it's necessary to clone the floppy controller perfectly. That should only be necessary if you're trying to make a drop-in IWM or SWIM replacement that works with a real Apple floppy drive. All that's really needed in my case is to clone the controller's CPU-side interface, which is documented in Inside Macintosh Volume 3, as well as the byte-by-byte floppy track data format, which can be inferred from the source code of Mac emulators or a 68K Mac Unix distro. In other words, by cloning the IWM + floppy as a single block, you gain the freedom to change the IWM <-> floppy interface into anything else you'd like.