Yeah, I'd seen you'd put together a MacOS flasher (which is awesome, don't get me wrong) but wouldn't you be SOL if you flashed a ROM on there that can't get you into MacOS? I was thinking essentially a "rescue image" which if triggered "somehow" would be able to pull a reload over serial with no OS dependancies. (Obviously any non-MacOS-booting ROM image loaded would have to preserve this functionality or the possibility of bricking it remains.)

Brain-dead hack way: split the ROM area in half by adding a switch that swaps the top address line, thereby letting you keep a MacOS ROM in one half and load experimental bare metal roms in the other?