Hi all,
first of all I have zero clue about coding.
How complicated would be something like this, if possible at all:
Addon "Transmount"
There is a box in each of your transmogs /maybe waorking with other transmog addons as well) that lets you choose a mount form your collection.
Example: My warrior has a T2 tmog and wants to use a classic mount, but one of the "hands" from SL for a SL tmog, and a Gorgon for a Venthyr tmog.
This addon assign a hotkey (or a macro with an icon), and everytime you presss that key you will mount the mount you have selected for your current tmog.
I am sure a few people would like this ;D