i 2nd this by adding in that the button could force a target change during bgbuddy. unless there's a plugin to make a smarter bgbuddy or somethin tho but i've seen it trying to attack things it can't get to and it just sits there forever. example is in Isle of Conquest, when someone drops in off airship and lands on top of the bosses building. often it tends to target someone up there and sit behind the building saying it's not in LoS and stuff like that.
A pause button or a manual overrider key would be most awesome... stopping and starting seems to cause issues and having to move or switch something to aid HB isn't rare (least in my cases) so i think this is a good idea