Indeed the Clevo MXM cards are wider than the MXM slot.
I also saw a company called X-vision selling new MXM cards within the normal footprint.
But then I agree, the cooling system must not be overlooked - every MXM can have the chip in a different place - how to design a set of heat pipes and/or vapor chamber that would fit a good number of those? Especially the future ones.
Another possible concern is power management - how do you tell the GPU to not draw more than 200W overall as that’s how much the interposer can deliver (at max voltage of 20V, I think). And probably EC/BIOS needs to also get involved to balance the rest of the power properly…?
But overall if this solution would be possible and would support at least some subset of cards, it would be really cool as this would make upgradeability so much more viable and worthwhile