I think it would be closer to 4 seats, not 9. Amtrak coach is 2+2. Replacing two rows of seats on ONE side would remove 4 seats. I think 3 rows of seats would be enough for a second accessible restroom.They also happen to be ADA specified. I am not sure how much seating space would be lost if a smaller non-ADA toilet was added. Perhaps two rows, so 9 Coach seats or 6 BC seats roughly. At the end of the day it is a tradeoff.