I would very much love this as well, and the NPC chocobos you pictured shows that such barding is indeed in the game's data. They would just have to release it. You'd also think it would be the default barding when they are not wearing anything, but alas 'tis not.

Start a petition and I'll make certain my retainers and I sign it^^

As a side note, it would also be really cool if the chocobos would lie down how we see them in the stalls when they sleep if we idle for a certain amount of time or lie down in the open world. It would make for some great screenshots while fishing or taking a rest!