Feature Request - A Better Shard Shop

Feature request......... if you already own a character at 7-star, can they be replaced by another randomly selected character in the shard shop? Seems stupid the game lets you buy 2 shards for a character at 300 shard currency, only to straight away sell them back for 30 as they're already 7-star.

Would also like to see the favorite icon appear in the store against gear/shard items for a character you have set as your favorite, so its easy to see what to buy. I'd probably buy more items if it were easier to see what I needed for my favorites.

Thanks