To me these seem to change some aspects of the original zone and quest chains.
I haven't been able to complete all zones in time but it feels like not all quests are available as they are marked for the non remix version.
I suspect they are missing completely but they might as well be locked behind the story line quests.

Is this worth treating differently, will remix be a one time thing that never comes back?

I have no idea. We might be able to mark quests with a "remix prerequisite" if we can detect that situation properly. However, I am not even thinking about that type of thing at the moment. Just trying to get a basic understanding of the new quests in the new zones at the moment.

All remix specific quests were marked as purple and important like the warband intro. This should give us a way to retroactively find them by questid.

It is more the contrary that is needed "not available during remix". Some Pandaria quests begin outside Pandaria for Pandaren and therefore the conditions can't be met because the character can't leave th Island. I'll upload things later.