Re: Fatal Flaw?
Jim, you are correct.
If you (or anybody) "updates" the definition of Protagonist or Main Character then, of course, it will take on a different meaning than what is commonly accepted. Your story analysis will make sense to anyone familiar with the revised definitions. (Casablanca would still be Casablanca.)
The good thing is a writer can write a good screenplay without ever assigning any specific labels to the characters.
The problem is that if you talk about your story there's the great possibility that not everyone would be speaking the same language.
BTW: Did you just update the definition of loglines to now include the sum total of the story?
"I am the story itself; its source, its voice, its music."
- Clive Barker, Galilee