Caporegime
My bad, misread what you wrote regarding MLU.
That is an interesting solution, especially once transparent LCDs start to get better - could integrate it into the focusing screen unit. The Fuji hybrid LCD relies on a mini LCD projecting the sensor feed into a square prism, but that's a tunnel OVF, so a transparent LCD would get around the need for a separate optical path for the LCD like Fuji does.
Another way would be to just have a smart port for a clip on EVF.
Or just don't bother with half measures and actually design an EVF only camera.
It depends on how they implement the EVF but at worst it will be like the X-Pro 2 solution.
Personally I prefer having optical, you negate the refresh rate problem, I find the EVF in the X-T1 to be adequate but I don't find it sharp enough and the exposure on the EVF not to be the same as the photo, there's not enough DR on the EVF to really tell you enough and some guessing still needed or look at the histogram.