I dont think thats a good idea, and i dont think it'd promote deck diversity. Imho, limitations are what promote diversity, for example you prefer to run crones with your deck which takes 3 slots out of the 6, and i prefer to take 3 other silvers and cut crones. If we both had 9 slots for example in silvers, we'd all run crones. Same logic applies for golds. You can run succubus/caretaker/kayran/woodlandspirit, and i prefer to run woodlandspirit/kayran/renew/ge'els. If we had lets say, 6 gold slots instead of the 4 we have now, you'd most likely put in a renew and something else, and i'd definately put in caretaker and succubus or gold weathers. So eventually nobody would have to cut anything, and they'd all take all the strong cards in their decks, instead of deciding what to cut now.
ps. Obviously, netdecking is a huge problem for diversity since people just copy paste decks instead of creating their own.