Allow Us to Adjust Passenger Height

It would be incredibly useful if we could adjust the height at which passengers sit on other mobs.

When making adventure maps, it is often incredibly useful to have one mob overlay another (For instance, one can make a witch that can be traded with by having an invisible villager ride said witch). Unfortunately, the height at which the riding mob is placed often ends up being a problem. (With the invisible villager and the witch, having them both ride on an armor stand sort of works, but the witch cannot walk around as usual).

My suggestion is either a number adjustment that allows how far up the passenger is situated to be fine tuned, or a binary option to either have the passenger at "riding height" or on the ground along with the mob they are riding. (With the second option, perhaps skeletons and zombies could also be made to stand when it is selected).