Of cavaliers and dracoknights; needing help with a FE styled campaign

[Nishant]

Howdy! I posted a while back about some racial subsystems, and have gotten those set, and have figured out how a way to allow the core classes to be tuned to take the theme of other Fire Emblem classes. However, I've found an issue; and that would be mounted classes. The issue is that there are more exotic mounts than just horses. Pegasi and wyverns are also mounts in this series, as well as griffons and, with the new game coming out, giant birds, though I can likely use stats of a giant eagle. The issue is figuring out how to keep these mounts relevant in late game, while not being broken in early game. Riding Horse, Eagle, and even Pegasus aren't too bad, with 1/4-2 CR, but a wyvern is 6; much higher than what I would put into mind... Any ideas? I don't want my players to feel like they can't make the characters they want, but I'm not sure how to balance it.

[Yorrin]

Sounds like you might want to tweak the promotion system a bit. Start out your flying mounts with Hippogryph stats and then after "promotion" give them access to bigger badder mounts.

[Draken]

You could set the mount to scale with the character's level in the mount-granting class and tie the math to it entirely?

Just have the decision between Wyvern/Gryphon/Pegasus/Whatever decide things such as armor class, attack options and movement speed. Hit points, ability scores and attack bonuses would be tied to character level.

[Jeebs]

One thing I've imagined was that a character starts with an old, battered pegasus (inherited from a parent or something) that's lost the ability to fly, and needs to be healed by a high level spell to fly again. It could start with a horse's stat block and eventually become a pegasus, or just gain a fly speed.

[Ceaon]

Fire Emblem treats mounts as a part of their rider's stats (especially in some of the older ones). You could just do something like that if that doesn't break immersion for you?