This would be useful for e.g. resizing button instance widths, but maintaining the link to the master component button height. See image for an explanation.

(And yeah, I know I can rig up something like this myself by going into the master component, putting an invisible rectangle behind the green button's rectangle, and then adjusting the height or width of the entire master component group or of the green button itself, but that's a pain. It would be nice to have this work on individual objects too, instead of just groups.)