Right now if you ungroup graphics that had a background or border set on the group and then undo the ungroup step, they regroup, but they have no border or background. This idea is to restore the border and background when undoing.
Eg. before ungroup:

After ungroup (Ctrl+Shift+G) and undo (Ctrl+Z):

Successive undos also do not restore the previous appearance; it just keeps undoing more things.