I think getting rid of rare farms is a good idea -- not just because they make rares so common, but because their losses as "top 50" decks could make newbs overestimate their own decks' power. (In fact, I was once newbish enough to build a deck with 11 different types of pillars, which then EM'd a T50 deck and won me a green shard. And I wondered why a T50 deck included an unplayable card, as I hadn't yet heard of farms -- or the automatic downgrading of spun cards.)
The way I see it, T500-deck creators would get a deck screen with 5 copies of the Oracle's chosen card already included (and unremovable), then would complete the deck with cards from their own collection. Each new deck would start out with a 250th-place score and would win or lose points, from fights with players and score decay over time, while its creator won or lost electrum from its fights. (Although I'm not sure what would happen if a T500 deck and its creator lost fights at the same time. Could the creator end up with negative electrum, and have to win AI1 matches to get back to zero? And could players who both create and fight T500 decks get matched against their own creations -- and improve those decks' standing by surrendering?)
On a completely different note, I'll now switch from an air deck to a time deck, at least until "air blitz" is added. (Zanz hasn't said anything about new time cards, has he?)