Right I think so too, but there would be no way to resize videos to automatically fit you have bezels?
If one knows the inside dimensions of the bezels its possible. I have code for this already that I wrote for a layout i'm working on that uses RetroArch bezels and their CFG files to correctly reposition and scale videos to fit the bezels, regardless of differing aspect or xy placement values
If its just a question of using one size for horizontal and one for vertical then it's much simpler. In that case one just has to look at the snap.subimg_width to height ratio to determine the aspect and then adjust positioning and scaling in a transition callback.
Yaron has my WIP layout already, and he can feel free to use whatever bits of that code that he needs. I owe him for all of the shader code of his that I've borrowed.