I may have overlooked it, but am I right when I say there's no camera file that would allow you to force the camera to follow a set of specific rules?
Sims 2 had a camera mod that made things Isometric like Sims 1, but you could rotate it 360 degrees, and the sound didn't work because as far as the game was concerned you were really far away but zoomed in. I'm wondering if something similar (but better) can be rigged for The Sims 3. I am well aware that it is ridiculous to try and make a fully 3D game go back to being isometric like it was 10 years ago. But there's just something fun about that camera angle.
Specific rules how? Couldn't you just change it so that it's default pitch and height was set to overhead? There is the VideoCamera.ini that was the old way of modifing the camera but now you can do it in .package format. Aikea Guinea makes the Camera mod I use.