Why do such a thing?
Well... Quite simply a standard Macintosh ii doesn't have a "proper" MMU, it has what's effectively a hardware shim - the HMMU.
This can be replaced with an actual Motorola 68851 MMU - which allows it to access more than 8mb of ram (I still have no idea if MODE32 works with an HMMU, I suspect not), and it also allows for A/UX to run.