Multithreaded Asset/Level Saving

On a big project, I might spend an hour building lighting, and then wait another 15 minutes for all the sub-levels and their corresponding BuiltData assets to save to disk. It looks like only one core is being used for saving the levels, though I see no reason why this shouldn’t be multithreaded. To be clear, the operation seems to be CPU bound, not IO bound, so multithreading should be a big help here.