FWIW, I do already have g1x mk II firmware 101a in my firmware dump collection.
It's DryOS 54p3, which puts it between the sx280 (r52) and g7x and sx60 (55p6). The other known 54p2 camera is sx700, which has been dumped but not fully ported. IIRC someone did some work on sx700 and got stuck.
I've included g1 mk2 in my test firmwares for
finsig_thumb2 development, so I expect it isn't terribly different from supported cameras.
