This is becoming apparent to us as well. We want an 8-passenger just for the 3-seat bench in row 2. The third row bench will be removed. Could order a custom 8-passenger for about $40K. We found a 2016 in Utah with our exact desired build and can get it for about $36K, except it's a 10-passenger.Even though the 10 and 12 passenger wagons are some of the hardest Transits to find both new or used, get the one with the seating you want in the beginning. The floor tracks are made to fit the specific seating arrangement so they are not easily adapted for adding seats.
Think it's worth taking it to a van upfitter and having the 3-seat bench installed in Row 2?