The register / recall function is something I've never bothered to setup for my 5D MK IV. Maybe I should.
Choosing the number of selectable AF points to speed up picking a AF point would be useful.
The ability to customize even more functions seems good on the surface, but unless all my cameras can have the same options, it can cause problems so I tent to leave things as default so I can go from camera to camera and not end up confused. I would like to be able to change shooting function remotely, going from Av, Tv, M, or P without turning the button. Access on the Q screen would be great. Unfortunately, it seems to be locked into hardware??
I really agree that the eye sensor is too sensitive on mine, just get near it with anything and it switches. That should be fixed.
The Fn Bar is useless to me because my thumb is usually resting on it, so it doesn't matter which functions are available since I turn it off.