The COG issue is quite true. Even the ol Raven case had a bottom mounted PSU even though the mobo IO direction is upwards. It may still be possible if the future case has universal mounting holes for freedom to place the motherboard tray and PSU on whichever orientation, but I think that would be too messy to design. Imagine having all the IO, PSU and panel coming out front, and all the other sides free for display panel and waterblocks...
I used to own a Silverstone Raven RV01 with the IO panel facing upwards. It was a pretty awkward but interesting build experience which I didn't get the chance to revisit. It would be nice for the next MasterCase (a full-tower, I hope) to be... homogeneous in terms of determining which side is 'up'? Gosh, I hope I'm using the right terms â€‹ I wonder if anyone else might be interested in this feature.