I'm guessing at the very least you could have a vehicle that can be made to look like a creature, that could possibly have a run cycle, then when you got off one solution, if the creature has to be static, is for the creature to lay down and sleep, considering the level of quality and animation for the mech mod I would have thought this was possible, but could it also be possible for a creature to function as a normal monster like livestock or a pet when not riding them and seeing as the mech mod's mechs can fire weaponry, im also guessing its probably possible to make mounts that can attack whilst being ridden. Just wondering if anyone knows if this has been done and of any limitations to this, if it is at all achievable?
There was a mod long time ago that made you able to mount creatures, i don't remember the name but it is possible. Chocobo mounts mod is an example of this but is old and i think that some things changed a lot.
Vaguely remember that one youre talking about... StarMount wasn't it? (http://community.playstarbound.com/threads/starmount.82174/page-27#post-2921996) Very much outdated, but still a very valuable resource as reference.