Can't people do these exploits with maxed cards too? I don't see how specific card level affects ANY of the 'exploits' you mention, and how allowing lower level cards in champ can be exploited more (again with the things you outline) than max level cards.
I love the proposal, it's YEARS overdue, but the level restrictions in champ are a bit much. I can't afford to buy a full deck right out of the gates anymore, and slowly build over time. If I buy a single bcx L I'd be pissed if I was not allowed to use it in champ.