TL;DR: Move house away, place TV on regular wall, remove the wall with "moveobjects" cheat leaving only the TV, move house back where it belongs.
Full thing:
OOOOOOHH I DID IT!!!
I spent the last few hours thinking of a way to solve this problem and I almost had a breakdown and now I'm thrilled to tell you that I SOLVED IT. I'll tell you how I did it and you figure out your way:
1. I had the same as you: a sunken living room, a TV placed on foundation wall and the sims wave and can't watch it.
2. First thing I did was to go on build mode and move the room somewhere else so I could easily reach ground level.
3. Then I built a regular-sized wall where I wanted the TV to be and I placed the TV on it.
4. Here comes the trick: using the bb.moveobjects on cheat, I did two things. First I moved up the TV a little bit with the key 0 (I'm on PC) because it was too low. Second, I took the hammer and tore down the wall. The TV remains where you placed it if you remove the wall. At this point, you have a TV floating alone above the ground.
5. I took my rooms and reassembled my house around the TV. I even placed a foundation wall behind it and applied a flat trim so it wouldn't intersect the screen.
6. Voilà. You can see it working in the picture. It will look like the TV is placed on the foundation wall, but it's actually suspended in the air by itself while there's a wall behind it. That's it. Hope you can do it too!
