When there is a summon storm event people complain. The possibility of receiving 7 star cards are so random. Some seem to be more lucky than others.
My idea would be a 100 card board. All cards face down. You spend summon stones to flip cards. The card you flip is the card received.
In the board it would say :
Cards in board 7 star - random number, 6 Star - random number, 5 Star - remaining amount.
Participants would have an option to flip cards, reset board back to 100 or refresh board to change the amount of 7 star cards in their lot of 100.
Refreshing the board would free. Resetting the board after any cards are drawn would be free the first time after that there would be a cost.
If a player is lucky and they flip two 7 star cards out of 4 in the lot in 10 flips they may want to refresh the board. Give them an incentive to not refresh. If the participant flips all 100 cards they would get a special summon coin. The special summon coins could be used for a special summon storm.