More Deck Slots
I feel like with the new expansions coming out, we really need more than 15 deck slots to fit all of our deck ideas. I've heard of so many people having to delete the decks they like to make room for new ones they wanted to experiment with, but that just seems so wrong.
In games like these, I personally find the building to be the most fun. I've already maxed out my 15 deck slots and written another 10+ more decks ideas that I have the cards for, but there's no room to make those decks without getting rid of my older ones.
Battling was my favorite part about this game, but I haven't done one since the last expansion came out ~1 month ago. Atm, it just feels like there's no incentive to do so, because I have no more room for new deck ideas which means I have no room for improvement.