10/13/2015 update here!
What I did was create a level loading system that I plop down in each doorway. It is visualized as a carpet in front of the door, Pokemon style. Click on the carpet, and the character will navigate to the loading volume on the other side of the door (you can also navigate to the volume manually, if you want.) Once you hit the volume, the map shows up, and the level loader decided which rooms to display and which to hide. Tap on one of the available rooms, and it will load the next room via cross fading. When the level is loaded, the character will automatically run into the room!
Most of this is automated, but there is some setup you need to do for each new room. But it isn’t that much.
Enjoy!
Edit: Ported the build to the Galaxy Note 4 I test on, performance is pretty good! 50 fps in normal rooms, and 35 in the dark room with the dynamic light.