You can set a material for a part to have a "Constant" Illumination, which means that it's rendered at the same color/brightness regardless of the surrounding conditions. Essentially, yes, it means you can model up a part to act as an indirect light, but it won't "emit" enough light to act like a spotlight or anything.
Rob helped me out with the whole "spherical wrapping" issue for the environments, and I ran a few tests. Things look a LOT better now. However, I don't think the wrapped image is acting like a light-emitting source (what an HDR image is supposed to do), which is kind of a bummer. Means I have to set up multiple lights to properly illuminate the scene.
So, I can use an HDR for the walls and get great lighting, but incorrect reflections (mirroed image is warped), or I can use a flat image for the walls and use multiple lights for a good rendering.
The answer is out there somewhere, just haven't quite found it yet.
Thanks everyone!