I could definitely use a feature like this. The ability to visualise different frames at the time of capture is appealing. Add my favourite 24:65 format to the list, while we are at it!
The thing is, this feature has already been programmed for a recent camera and integrating it to another one (assuming they use the same operating system, EVF and have a similar processor) should not be a huge deal or result in more costs for those who do not need this feature.
It seems to me that camera manufacturers have not fully used the potential of customisation that could be done by the user, considering the flexibility offered by EVFs.
For instance, in a Sony A7x camera, it is not possible to display the two axis level indicator and the luminance histogram at the same time. It is either one or the other. We can also have one on the EVF and the other one on the external LCD screen. I wonder what prevents them from displaying both on the EVF?
Cheers,
Fabien