I can understand the wish to be able to zoom in x and y direction idependetnly from each other very well. Because this is something, that has to do with the individual requirements and taste of each user. A lot older real tec media player featured that function. And Kodi itself features it, too, given by the zoom + pixel ratio function.
If you want to eliminate the black bars on the cinemascope, you have to zoom in vertical direction ~30%. If you zoom at the same time in horizontal direction just 20%, you keep a lot of the content and have almost no visible non-linear stretch effekt. And by that you can transform any movie content to a 16:9 screen.
@Futeko, such a function would make your'e products significantly more attractive, you should definetly think about implementing it.
rgds, Holger