what for? so that you can play them and crash the game? people will expect them to work if you display them.
they should simply flag some minor patches and let them play earlier replays.
uh for those technically advanced enough to know how to revert back to the old version.
(this would be very useful for casters.) also maybe allwoing you to download previous verisons of the game off there site so you can play those older replays. agian mostly for casters or anyone who wants to view the old replays.