Post expansion ideas.

[Vorx]

Not so much clones Johaandr as more classes, the Squall gem for instance would add a Gunblade style class and with them adding Blitzball in the expansion the Tidus style would go well with it.
Over all this is a may to use the Soul Crystal system more as its barely explored as of now with just the Job setups. This idea would add more options and styles for people to pick.

As for balance like Viki mentioned that is why in the listing i placed the characters in the section they were in, even in their own games this is where they would of fell into so the balance is already there.

[Settiesama]

and with them adding Blitzball in the expansion the Tidus style would go well with it.

They joked about it, and said they had ideas, but never once said "we are adding it". While we may see a FFXIV version of Blitzball in future, it will be vastly different from FFX's (this bit was the only confirmed part of it).

As for the idea, you want them to add in running motions of fighting styles of historical characters, when chars like that are confirmed to have to travel through worlds. How would they have soul crystals? How would they have their movement etc inside the crystal (The jobs we have now use the actions of US, not the crystal)? How would they ALL have come to this world? I'm sorry, but this is just a terrible idea, the cameos are more than enough.