Saying that Hal, look at the size of some of the creatures they managed to stuff in there.
Rio, anything to do with that is unknown at the moment. I know quite a lot of people would love to be able to drag around a pet, or even feed their priosners to it (combat with creatures in your party, yay!), but that will be decided when everything else is coded.
Srukk, I asked about that when I did a little work on creature rules. The problem is that you'd have to set the creature as a container, just like a vehicle. So you'd ride 'in' the dewback, just like you ride 'in' a swoop as opposed to 'on' it.
A little wierd, and apparently quite a hassle to change the code to do it any other way.