I'm still not at max yet, but I would love it if they could find a way to do this. Even if it was something as simple as instead of just retiring your chocobo, you could "let it rest" or something, so you still only had 1 active at any given time, but could switch between your currently active chocobo, probably with some kind of MGP fee and/or cooldown on it. Having more than 1 active at a time probably wouldn't work very well now that it's part of the DF though, since there's no "select your ride" type thing that would work via DF.