Has anyone here ever attempted using the screenplay format with lots of tweaks for writing a novel? I'm not talking about just writing a screenplay, but something interstitial between the two.
I've seen it done once before, differently than how I'm doing it. But I'm not sure how disconcerting it can be for a reader. Would this be a major turn off for most people?
I don't think many readers have read screenplays, so no worries there. The only thing you might want to watch out for is that for many people, the only time they've read something in a different format, such as a play, was in school. People tend to hold pretty strong opinions about things they've done in school, so it may instantly attract some people but scare off others. But it shouldn't be too much of a problem.
Most people may not have read full-on screenplays, but they've probably had some exposure to playscripts in school. Media/pop culture magazines like EntertainmentWeekly sometimes have a bit of script-format as an illustration. I'd bet that most people would recognise the format: Name, colon, speech, other name, colon, other speech.
I'd skip a professionally formatted screenplay in favour of a simplified format, though. And, is there some way to introduce or explain what you're doing, to sort of prepare readers for what they're about to see?
I have no idea what your story is like or about, but I can think of a couple of stories where screenplay (or a hybrid) would be an interesting choice:
MC has an adventure, and this is the movie they made of it (this would be good if there was some conflict between what actually happened and how the scriptwriter has interpreted it).
Movies are influencing or reflecting the MC's life, and snippets serve to emphasise this.
Story (any genre) takes place in Hollywood, and, again, the screenplay format emphasises it.
Good luck with it, sounds interesting.