It's been a problem for a long time; making units playable is a slow and boring process, as you have to do it one at a time, selecting each unit and making it playable.

Being able to make an entire group playable (when you drop it in the editor) would make this process much faster.

Other methods of mass-switching of variables such as playable/non-playable, skill level, etc would be good as well, but I think this would be a step in the right direction.