Since the original model is pretty limited and well... ugly, it would be nice to create your own.
I know we have custom interiors but it would be much better if we knew how to do them. For example, I LOVE the original TARDIS but I also want rooms in it, but the only interior providing that is the Hell Bent interior which is very tricky to use in first person since it does not say any of the switches. I'd love to make my own but I have no idea how.