I printed some interiors for Williams coaches (bye-bye silhouettes!). I'd created some previously by printing seats and gluing them to styrene sheets, and fashioned the bulkheads and corridors from styrene, but this is much easier.
No reason to print bathroom detail that'll never be seen, just enough corridor so it looks like there's a corridor at the ends of the car. This is printed in 2 pieces, which join together (interlocking tabs) where the central posts are. The floor centers are raised 1/8" from the edges to allow wiring to run underneath. The "bathroom" area will be used for lighting electronics and connectors to the LED strips in the roof. Keeping the bathroom windows, adding acetate windows along the rest. Shown here printed and cured, but not yet painted. Both pieces print at one time, so it's about a 4 hour print job per car. Seating layouts for other type cars can easily be put together and printed if desired.