Would love the ability to catch mobs out in the field .. stable them and breed them for a unique personal mount.
Making them MB sellable would be a must as well.
Since too many limitations and too few choices = disappointment..they could hold off until they had a large pool of "possibilities" ready to go!
Certain limits would have to apply I assume like usually sticking to the same species ..but....SOME "oddities" should be definitely be allowed to keep things even more interesting.
I would enjoy having to catch a male and a female ..and over time by caring properly for each, result in them mating and end up with a baby mount to raise to adulthood.
Not saying these mounts would have to end up as companion fighters like our chocobos (even though that would add a lot of nice variation to the game) but even if they were just mounts at the start would be sufficient.
We would have to teach them to fly, swim (one day) and exercise them properly to reach max speed etc. They too could have color changed with the current design.
SE could broaden the way to achieve a fully developed adult with many cool quests/repeatable training etc/special foods to enhance a special ability until maturity...making use of the chocobo race tracks etc O.o
**I get that this would be very difficult to design properly ..a nightmare probably lol** BUT if they could master it and have unique mount designs, colors...maybe even abilities...it could be really cool.
And potentially add something in their game that would be unique to ffxiv only (as far as I know) especially if they designed a few "oddities" that are truly one of a kind through experimental breeding.
Also I think adding a few craftable / "non living" mounts to certain professions would be enjoyable (without the need to make mats as insane to get as wool tops though...keep it realistic se..should not a lifetime goal errr...)
Anyway just tossing the idea out there..no biggie either way but something I have always wanted in a game.