Thr problem is the lack of battle winners to survive the entire set up. I, as well, would love to see decreases become stronger but for now, with so many cards you would have to have for it to reach its potential, you wouldn't have room for much battle winner enhancements.
I was thinking about it... if Cactus was to make this theme stronger... the key is evil characters that power the defense, so your enhancements can just be decreases with a few battle winners.
Brown EC - Immune to all heroes with a reduced toughness. Cannot be prevented.
Brown EC - If blocking a weakened hero, the first evil enhancement played cannot be negated.
Brown/PG EC - If the block is successful, all weakened heroes in play become paralyzed, and may not enter battle until healed.
etc.
