Line 1 also has "walkthrough" = articulated trains.
Perhaps changing the seating arrangement--one row of seats on each side, facing the center of the car, would allow more standees.
The current arrangement only allows "comfortable"
standing near the doors.
It's a difficult balance to get. You want to provide comfort for longer journeys, and those off-peak, while providing sufficient space during the peak. I think every urban rail operator goes through this quandary!