It has its merits to try to reward users with leveled up cards, but it simultaneously makes zero sense to punish players with lvl 1 cards. Take Riftwatchers for instance; I was stoked when they were released because they are NEW cards, with new cool ways to play opening up for me. IF you nerf players with lvl 1 cards you will also basically reduce the joy and excitement of getting new cards, since they will earn less if you don't buy like 14 copies...

Why not just get rid of the starter cards (as mentioned above after an introductory period) and then let the best player (or bot) win? Increase payouts to card holders based on bcx if that is of interest, but don't punish the skilled players who can beat higher-leveled cards.