I don't like the idea of a mount/animal/critter as a battle companion (sorry, my adorable Chocobo!). I'd rather have that snooty Elezen I had as a Path Companion in 1.0, or a cute Miqo'te, or a feisty Lala, or a cool Au'ra . . . well, you get the idea. xD

It would be neat if we could use our retainers as companions! We can already gear them and customize their look, and send them to do battle-related errands for us.