I'd buy it. If you think about it, there could be three playing modes available. FFX, FFX-2 and the more traditional sports game version crazybayman suggested. Most of the graphics and sounds would be used in all three so there wouldn't be much repeat effort to develop a three game title like that.

And to those who compare one title to another unrelated title, your argument basicly is "That sucked, so this will." which is not a logical argument to make. We allready have a popular game that can be fully realized as a stand alone game if developed properly. It has a built in untapped fanbase. And since it crosses genres you might be able to draw some Sports gamers to RPGs. "I like sports. I like Blitzball 2006. I'll go try the game Blitzball was introduced. I like Final Fantasy. I like RPGs."

I have no doubt that such a game will at least pay for itself and grow the market for the FF series. If it is a smash runaway success it could radically change the landscape of video games in the years to come.