Mystery Gifting Suggestion

Hi, just a suggestion I had. I gifted my husband a mystery champion and he got Azir. However, is one of the champions he had refunded after purchasing a while back. Since our refunds are so limited as it is, I feel bad that the mystery champion he got was one that he'd previously refunded. I think it would be great if the champions that someone had refunded were removed from their champion pool upon receiving a mystery champion :D