Can't use a different mount with Chocobo Companion out

So I have 4 different mounts besides my GC Chocobo Companion and I can't ride any of them while the companion is out? Why not? While I was questing (which I probably won't do again until the level cap is raised), it was irritating to continually dismiss and resummon the companion, or spend the time to evaluate if it was worth 30 gil to do so or not. That's not much fun. It would have been way more fun if the thing would have just stayed out (like a real party member) regardless of what mount I was using.

And while we're at it, why can't I ride the thing while not in battle with it out?? Isn't that what you'd do if it were somehow closer to a real life scenario?