That's what I want to hear. A good card, in my opinion, should be powerful only when used in combination with other cards. I just don't want this card to be overpowered by itself.
Okay, you can use it every other turn, and you need to buff it in order to copy your big creatures. Well, Aether doesn't have anything to buff it's power, so you need to splash a second color already. So how are you going to buff the Pegasus, and what are you going to duplicate? Let's say we use Aether/Light for blessings on the Pegasus. Well, we've got slim pickings for duplication targets. We can't use rage potio on the pegasus alone, not without blessing or armor, so we're up to 3 colors. Basically rainbow, and rainbow decks could probably just use the aether quanta for 1 PU or Fractal and do just as well.
Personally, I can't imagine a deck built around this guy that would be a gamebreaker, but he would be a useful addition to some decks, and that is how I hope all of my mount designs will work.
Jallen