Making Colorful Feather available for bound dias

I've reached tier-9 wings recently this morning, and I have no idea how to get colorful feathers which is only through diamonds... As a suggestion from a Free-2-Play player if you could include colorful feather on bound diamond tab in mall. Guess the cost would be high, as long as its buyable through bound diamonds. It'll help all players not only Free-2-Play players who'd have tier-9 wings. Hope you grant this suggestion, thanks.