Sorry for all the clarification questions but hey, that means we like to play and read right?
It states in the AS book that you can board anything with the LG special. However, mechs have their own separate chapter on what they are capable of in the AS companion. Size 4 + LG mechs don't have a CRW# special so they also cannot repel boarding. Also it states that these mechs can only carry BA like a normal mech. If you can board them, what stops you from infinitely boarding your own infantry and call it a repelling force?
Thanks!