Krita should support drag and drop into the Layer Stack. It would be easier if you could place the images where you want them in the stack instead of having to just throw it on top and have to move it later.
That should be possible (as in, the action "drop on canvas" and "drop on layer stack" are distinct) and yes, it can improve usability. The only problem would be, should it be a File Layer or Paint Layer? But it can have context menu, like dragging on canvas.