This is mostly a quality of life suggestion for people who would prefer it that way and to fix your menu-back.png blocking you from clicking your score on a map if it's too large.
I once reported something, that the back button gets priority over other stuff if it's larger They replied It's too big (or something in the lines of: Make it smaller)
Skin makers are responsible for keeping their sprites within default dimensions.
I don't know about switching the interface. It would be a lot of work to get it working properly. It's hard to say it would work completely with the way Song Select is designed. Group and Sort look like they would overlap with the mapper's name.