I can and have done already with Gerry. I also made a Baby Desert Fox xD
The problem is the character animations. There are several mounted animations, like for when you are running along, jumping, idle animation etc. and I have to try and match them up with the size of the mount and it's movements. You can never match them up perfectly as you can see with the Gerry mount and there are no tools that allow you to edit the models/animations that Iris uses, yet at least.