I think what he's asking is if you guys can change the weighting on buyable cards to favor cards not within peoples decks. Also it seems like he's asking for them to not repeat but I'm assuming that the system that defines what card shows up is entirely random so not sure how that would be implemented unless you popped them off the que
I am not sure that would work, you might not have the card, but your friend does have it, so who do we favor? We would have to make all players see different cards to get something like that working.