I have always thought that it should always be any card ever printed should be legal. It's been one of my pet peeves about this game that they keep changing the rules (ie what's allowed, what's not, how to mulligan, how many cards to play at the start up....used to be you rolled a dice and if you won the roll then you got to go first, none of this if you go first you don't draw crap. It was plain and simple).
In my mind, they have always just pumped out the cards to make money, not because the cards added a whole lot more to the game. The game has changed so that there are so many variants and rules now that it's intimidating to new players (and to old ones that have been off the scene for awhile.... my dad used to play all the time. Now since he has been away from it for a few years he is reluctant to get back in because he feels that too much has changed and he doesn't want to look like a noob when he really isn't. And I don't blame him because I felt the same way when I came back into it).
I think that if you make a card then it should be playable, plain and simple. Perhaps restrict the lethal combos (ie instead of banning a card, ban what it can be played with in a deck so that you don't have those situations arising that made the cards banned in the first place). What was the point in even making the card otherwise? It would definitely make the designers have to stop and think more about how certain cards play well with others. None of this "well if it don't play nice then we will sit little Johnny card in the corner for a time out".
I payed good money or did good trades for some cards and now all that has to happen is let a few years go by and my good money card(s) becomes common because of all the reprints or the changes in the rules that make them practically useless. It's kind of disheartening really. It's set up so that if you want to play in legal tournaments it forces you to dish out money and buy the latest cards. I guess that's why I mostly prefer to play at home. Then I can play my favourite cards that I have had for years.
I probably wouldn't go for the ante thing either, but I definitely like the idea of playing with anything that was printed.
Sorry for the rant. I think that is all my pet peeves spelled out in one little rant session.... I think.