Maybe this could be solved by having platform doors that open in all the required positions? You could either add extra platform doors or make platform doors t

Maybe this could be solved by having platform doors that open in all the required positions? You could either add extra platform doors or make platform doors that are wider than the train doors and open part way to match the train. Unfortunately, if cars have different lengths, it increases permutations a lot. But you could handle even that by building a wall made entirely of doors (staggered on two door tracks), so the gap between any two doors can open up to any desired width.