Maybe Lancers could become "mounted" combatants, with multiple branches of advanced jobs:

Wyvern Knight - Gets a wyvern that can be ridden!
Chocobo Knight - Gets a chocobo that can be ridden.
Cavalier - Gets a horse that can be ridden.

Give bonuses to the party's combat while the * Knight is mounted. Granted this would make them stronger outside of dungeons than in, but this is an idea in progress.