i think if you work really hard on a pet and get it to epic it should become a amount you can ride. not just a pet with a card to use in combat this would make working on your pets much more rewording. consider this for crowns pets only
Though that is an awesome idea, it would be difficult. Imagine riding a pet like a sprite, or an ice colossus, or an imp. It would be rather hard. What you could do though, is have some pets (the four legged ones) grow larger and larger as they grow from baby to epic and eventually have the ability to remain as pets or become mounts. (I'd love to have a fire cat mount). And the others grow larger and larger and eventually have the ability to remain as pets or become morphs. (not like the poly morph spells, more like the ones in the crown shop.)
You never know.The editors at wizard 101 always improve the game. I for one think that you should have the option to choose (when it gets to epic) leave it a regular pet or change to mount. Just a little something to think about.