The thing about screenplay format is that people who aren't familiar with it sometimes just find it to be "all dialogue" with little, if any, "descriptive narrative." Also, if you're going to include notes/stage blocking in it that could be a distraction for people who aren't used to/familiar with it.
Now depending on the way the fic is done and on how the actual reader reacts to it as he/she reads it, it can be anything from a raging success to a massive failure. Not everyone "needs" descriptive narrative in their stories, but there are others for which it can be a must have as it is often used to provide insights and descriptions of what's going on that you just can't achieve through dialogue. Don't get me wrong, dialogue is also essential in a good fic, but there's only so far that it can take you.
Problem here is, it's one of those things that you can't really know for sure unless you actually try it. My suggestion would be to start small, like with a one-shot, and see how that works. When you post it, make a specific request at the start of the entry for readers to comment on how they find (i.e. whether they like/dislike/etc.) the screenplay format.