@lawrie If you have a working implementation on Mister to guide you, maybe it is not all that difficult to add mouse and disk.
The wikipedia page for the original Mac's describes the mouse, including its wiring across chips:
The disk hardware is essentially the same as the disk hardware on an Apple ][:
I think once the registers that the controller presents to the software are known, doing a verilog replacement can be similar to what you did for the QL.
Oh - just found the ultimate hardware description here:
And a ROM disassembly is here:
On the Mac, the rom just contains start-up code and device drivers. On the QL, it contained the whole operating system. The biggest part of Mac Plus rom seems to be the file system implementation.
I'm not sure that is correct. See below link for some details:
floppy.vin the source code archive on that page). It seems this project was doing exactly what you are aiming for: a quick fix to get something running. It also has a preprocessed system disk image in the archive).