Is there a way to make old replays viewable?

I've been browsing through my old replays and noticed some of them were not available for watching because they used an old version of the client. A quick search took me to this page (and this announcement), which say that all replays that predate the hotfix discussed there will not be available for watching.

Alas, the replay I want to watch most (I stole the boss in the Sky Temple from under the nose of the enemy team) is from version 13. Is there a way to modify the replay file to trick the system into believing that it's a more recent version of the client? I tried opening the file with SublimeText, but it's encoded, so no luck there. Maybe a special tool, or a script?

In order to play the old style replays, you need to run them in the same version of the client that generated them. That way, the system could make the same decisions as it originally did. Every time they updated the client in a serious way, the old replays would stop working. There's not just one old version, there are many. If you did trick the system into playing an old replay, it wouldn't look right. The AI would make different decisions and the scoring (damage, etc.) would be different.

Blizzard changed that for the newer replay system. In some way, the new system either preserves the older clients or is client independent.

Unfortunately, to update an older replay to play on the new system, you would need the older client that matched the replay and an update script (that Blizzard would have to write for each previous client version). It's unclear how difficult it would be, although Blizzard has indicated that they aren't going to do it. The suggestion being that it is too difficult to be worth doing.

You might be better off looking for old versions of the client. The problem is that the way that Blizzard developed it, update is automatic. So people may not have saved versions of older clients. You certainly couldn't play a game with an older client, but you don't have to connect to the server to watch a replay.