10 bit up to 4k 120p would be expected for me. Canon and Sony are doing it with full frame sensors. Good low light performance is expected and IBIS.
To really change up the game, some sort of 12 bit recording or E-ND would be huge and really give a big reason to stick with M43, even if AF still sucks.
I don't know. I expect crippling on lower end products. Just not the extent Canon does it. Making a $4000 Camera only do reliable line skipped 4k in 2020 is silly.
The difference between the Canon C300 MK3 and the EOS R5 is huge compared to the difference between an S1 and a EVA1 imho.
A pocket 6k/4k rig isn't that crazy. Sony NPF batteries mounted to a half cage on top do the trick. A monitor is definitely nice but not 100% necessary. Most of the gimbal shots I do I stay the same distance from my subject to avoid focus change.
A Fuji XT3 or Panasonic S1 are also good options for you. Definitely a jump up in image on both those cams from a C100.
All the Fuji primes are awesome. Viltrox is a good option for something a bit more affordable. The 16mm 1.4 and 23mm 1.4 are pretty legendary. I love the 50mm f2.