It would be fun if, the smaller raced could ride on the shoulders of the bigger races. Say Lalas riding on Rog's Shoulders.

I like in FF that Chocobos are the standard mount. I also like original mounts (the Gobbue is a pretty original idea for a mount)

But i'm a little tired of Tiger, Lion and Wolf mounts. I know they often look fierce and neat, But unless they can be part of the Chocobo "buddy" system Yoshi-P has been talking about i'd rather see some mounts farther out from left field. Some Examples:

Some sort of Buffalo or deer.
A Goat.

If they ever make multi player mounts:
A centipede with 3+ Saddles on it.

Some interesting things i've not really seen before as a mount.

But i think Red XIII as a mount isn't something i'd like to see. Would really cheapen him and his race to me. If anything i'd like to see a playable race somewhat in his image/style.