Shards suggestion

KNEEBLER

I'd like to suggest giving players the ability to control their shards more. 
We can favorite a character today, sure.
As I've played event after event, I am collecting shards for many characters that I will never really use.

All the while I'm struggling to get a few characters which I enjoy.
If I could sell shards I've collected for some characters to be automatically dumped into my favorited characters, I'd be able to build up a few characters better. Of course, keep the shard exchange on an even level. 5* to 5*, 4* to 4*, 3* to 3* 

I don't think it would break the game per se, just allow some players the ability to build up a few characters they really like.
For me, I could sell all the 5* shards I have and get maybe 3-4 covers of one targeted character.