Multi level cars, seats?, inventory areas?

Add stair support (in case, it's for multi-level cars and other locomotives) and it's up to you to add beds so people can take sleep inside the car, and one more suggestion, the passengers or other cars have a feature where it does not allow mobs to get inside. it's a good idea for players who are sleeping inside the car with a bed.

Opening doors on locomotives or cars. and also add supports for seats for players to take a seat.

you could outline these materials (just like BOGEY_FRONT and BOGEY_REAR).

DOOR_ID#
BED_ID#
STAIR_ID#
SEAT_ID#
LADDER_ID#

All you have to do is just figure it out the system for these systems above.

EDIT: many rail cars and some locomotives have ladders, so it would be nice to climb up on top of any rail cars.