Why not just a room in where it's intended purpose is to watch some form of display, and utilizes an adequate sound system to simulate a theater surround effect?

Who cares what the source is, and why does it matter what quality of equipment is being used? Sure you can dress it all up with automated lighting but that certainly can't be a requirement.

For all the possible set ups and available equipment, you could spend the rest of the year coming up with different versions what a HT is supposed to be and/or have, and each would be just as correct as the first few hundred.

I think this subject is too easily converted into what you believe a home theater should have and not necessarily what it should be by definition. With that being said...lol, I would never consider a room with any natural light source a HT.