> It rather directly faces a deontology vs. consequentialism question... if two different processes (distributing changed contents directly vs. distributing patches to an end user and providing combination software) produce the exact same end results, on what basis will the law decide that one is OK and the other is not, since allowing people to distribute change lists provides an effective 100% workaround to the existing illegality of distributing changed works?

You're going about the question backwards.

If we were basing things on reasonable consequentialism, then downloading a modified version of something you already legally possess would not be a copyright violation.