I can see this going a few ways:
1. They concentrate too much on the jump scares and the animatronics themselves and end up making something awful and too much like Saw (so just blood and gore, no decent plot that makes a bit of sense without the gore)
2. They concentrate on the animatronics still (mainly the ones from the first game) and wind up trying to give them personality and relatable for some reason? Which... also wouldn't end well.
3. They do the decent thing and make a movie solely about the plot. Either start from the second game and work forward, or start from the first game and give flashbacks to the second game concerning the actual murders. Perhaps Mike sees Golden Freddy and starts trying to figure out what happened, leading to him researching into everything. He'd have to do more than just sit in the office, after all. They also run the risk of trying to do too much, considering there's three whole games. They could touch on what happened to PG with flashbacks, though, and just not do the third game because they can do the whole of the main story in one film.
That said, they might not do anything like that last option, which means it probably won't be anything I want, so. Yeah.