The exterior walls are fiberglass, foam insulation and luan--I guess run through a roller and laminated together, with some aluminum here and there. They seem to be strong and sound, and I don't want to mess with them.
But the interior walls are another story. This wall between the living room and bathroom makes me crazy:
It's framed up with 1-by's. Kind of like a Japanese paper wall, only not as cool. I am 90% sure that the luan you see on the other side of those "studs" is the back of the bathroom wall. And yes, it wiggles if you shake it:
If you look closely at this photo, you can see darker luan (between the wiring and the bright luan on the right)... that's the angled "wall" behind the toilet:
See? I wouldn't make this up:
There are a few good reasons to open this up and rebuild it. First, I have two alternative plans for the bathroom, and one requires an actual wall, not a curtain of paneling. Second, I'd like to make that wall substantial enough for some shallow built-ins on the living room side. Third, I'm so close to being able to see a lot of plumbing and wiring, I'd like to go ahead and know exactly what's where.
Here comes the can of worms...
ADDED: That huge cabinet I removed gave this wall some strength.