So I have read about the whole suggestion about downgrading cards, and I think its a complicated solution to an uncomplicated problem. So I came up with a uncomplicated solution.
PvP Duel 2 (No Rewards)
What is it you ask? It is simply the exact same as the original PvP, However, only unupped cards, and all upped cards are automatically downgraded for the battle. Just like in PvP 1.
Simple Solution to a simple Problem. That way anyone can use any card in unupped tournaments by putting in the upgraded version.