You could do some trickery where you have an invisible object like a Tiled Background or whatever that you use for collision purposes on top of your Solid objects. Set your solid objects collision mode to None, then use the invisible object to detect whether or not the space is occupied. When it is no longer occupied you can change the solid objects back to Per Pixel or Bounding Box or whatever.
I know it's kind of cluttery having extra objects like that but without being able to toggle the attribute it's probably your best bet.