Why would you want such a "multi aspect sensor"? I would prefer to use full width of a 4:3 sensor for all aspect ratios higher (like 16:9, 3:2) => better resolution.
This is what GH5 does: 4:3 is 5184x3888, 16:9 is 5184x2920, 3:2 is 5184x3456 but 1:1 is 3888x3888 (as constrained by height of sensor).
For video the full sensor is used but the output is resized to the mode (HD, UHD, C4K, 6K).
With just 3D-lens on washers, and no toe in prism effect, I typically get almost HD (~1850wide per side) video for my subjects AFTER registration using C4K mode. Stills are easily above 2000 wide for most subjects not too close. Real close requires toe in to get above HD. If you had perfect toe in, the LR resolution would be about 2400 x1350 or 2400 x 1800 for 16:9 (my standard use) and 4:3, after cropping out the septum effect.