I think that allowing all those at once might be a little too powerful, actually.  Torahime’s Change Shape ability only allows her to transform into a medium or small humanoid form and doesn’t actually cause any physical changes to her stats or allow her to get anything other than Extraordinary abilities of the form she changes into, so just giving the castle movement modes (a land speed and a burrow speed, perhaps?) and the ability to change its outward appearance should be more than enough.