When different art for upped/unupped cards was brought up, Zanz mentioned that he could do it by keeping the information off site, and it would just have to retrieve it for use. He said this was a bad idea because there would be loading times whenever the card's art showed up (unless I misunderstood). If this is the case, he could store this information off site. I would love this implemented, and I wouldn't mind a little loading time in order to see it.
Also there are multiple ways to do this, it could just give the deck code the game played, and whether it was a win or loss, or a turn by turn play through like Xeno's simulator. The latter obviously takes less space. The only bad thing I can think of, is that this would allow arena-builders to adapt to the meta much, much faster. Although I wonder now if a faster evolving meta is a healthier one (it is argued that a more fluid economy is better).