In a case like this I don't think there should be any penalty beyond the one unit or building that is disbanded or sold. This is not an example of a team trying to exploit game mechanics. I suggested (a few times now) that whenever a team gets a pop up saying a unit was disbanded or a building sold then they should inform the admins who could then investigate and give out a punishment
if warranted. Let the admins decide if there was an infringement of the rules, how big a transgression occurred and what punishment (if any) is appropriate. Even when someone is killed in RL it could be anything from premeditated first degree murder to negligent homicide with defences ranging from insanity to self defence. We're agreeing not to purposefully run deficits to exploit a weakness in the game code, we should live to that agreement and let the admins be our judge and jury if problems arise.