This is a really good idea. And since you wouldn't need to add them to a "scroll" anymore, it shouldn't be too difficult. Would make a lot of sense to add old giveaway ninjas/seasonal ninjas. Maybe really old ones like the cats or Sasuke Suit/Sakura Cloak, Chiriku that are really old for Survival coins, and more recent ones for moon coins or group coins. Might even do 4 different ones each month, one for sun coins, one for moon, one for group, and one for survival coins.