Elephant in the room is obviously, what you see is what you get, there's no way (to my knowledge) to move the Reference Image around or scale it for that matter, which is why i think it's probably underused by now.
So i think either you could integrate the feature as a layer type in the layer menu or just have a separate set of controls to move, rotate, scale etc. the Ref Image around. The layer obviously won't be rendered. As i said, having the image both on top and below the drawing just is very helpful and to be able to turn it off and on with one shortcut is really handy as well so i hope you give this old feature some love ^^
Okay, now cue "There's a script for that"
