Reversing seats
Unfortunately there's more involved than just reversing the seats. The pax load in a forward-facing seat is taken by the seat belt at hip height. If the seat is reversed to rear-facing, then the pax load on impact is taken through the seat backrest and not through the belt, with a consequent higher c of g for the load so more rotational load trying go pull the seat out of the rails. Therefore, the seats and floor have to be beefed-up if rear facing and this will add additional weight.