Surely common sense is irrelevant here? Playing a banned player is cheating and we could, no WOULD, have scored the 6 goals we needed to get through had he had not come on in the last 2 minutes.
We were robbed and to be honest I think we should probably be reinstated directly into the group stages rather than have to go through the inevitable pumping in the qualifier. As further punishment, Legia should probably also give us any of their players that'd improve our team. So basically we should get all their players.