I'd love to see a way to obtain additional copies of the Achievement Emblem apparel. I don't mind them being soulbound, but maybe add a crafting recipe or a special "achievement shop" where you can buy more of them after you've unlocked them?
I like the idea of repeatable achievements..! Not just to get more copies of the apparel*, but also for a more steady stream of earnable moonstones. While yes, achievements award some, it is a limited amount. Once you've completed them, that's it. That is hardly a long term way to earn moonstones via gameplay. The achievements definitely need to be more difficult than the daily tasks at the top of the screen, both to avoid them being very double, but also to actually make them worth rewarding moonstones.
*big no to them being soulbound though.. Soulbound stuff absolutely kills the economy, which currently already isn't in a good state.