If you can get a person to describe the Bible as a book, I think you can get a reasonable approximation of the person as a whole. “What do you think of the Bible?” Find/replace “it’s” in their answer with “I am”.
The more exposure they’ve had to the Bible, the stronger this relationship will be. An answer from a person who’s never opened the thing and can’t name any of the gospels will signify nothing about them except vapidity (which should have been your default assumption anyway).
A small fraction of people will have no opinion due to ignorance (it’s occasional, but it does happen), and their answers won’t signify anything.
I’m imagining a simple test with a simple head-fake very like unto the Maykorner test. (By the way, you should know that this is why employers are asking you “which animal are you like, and why”. If they had any sense they’d be stealthily administering 10-word vocab tests.)
“What do you think of the gospels?” This should reveal their attitude toward God and natural authorities.
“What do you think of the prophecies in the Bible?” This should reveal their natural attitude toward the supernatural, and predict their first response to witnessing a miracle.
I think I’ll expand this into a full battery and stress-test it with some responses. I’m hoping to filter the entire ideological spectrum into a useful shorthand.