I don't know if this feature was announced, but I sure was surprised when I noticed "Newest" "Old" and "All" tabs on my planetary improvement list. So instead of having to start new planets with Enhanced Factories I could still build basic ones and then upgrade. Definitely adds to the micromanagement but also cures the "factory-phobia" that always had me putting off factory upgrade techs until later in the game. Also, as I conquered / influenced other civs' planets I noticed they were using older buildings too. The AI seemed a little hairy about the whole thing, but then again I even had a hard time figuring out what the best balance of old/new was.
Either way KUDOS TO STARDOCK for another asked-for but unexpected feature that is making Dark Avatar pretty much the most comprehensive expansion ever!
Not to mention the new ship jewelry and the blank hulls integrated into the game!