Paul should have a bigger part in the final movie
Paul had a rather brief but strong appearance in this movie, just like Mick had done in the original.
I think for the next they should focus more on him overcoming his insanity and perhaps being tracked down by the victim from the first movie.
There would be an irony: the fact that Mick allowed him to escape would be his downfall.
There's some real truth to this as well - a lot of serial killers, by the time they've killed say 20-30 people, they get very careless about their work, and those kinda mistakes are what help to incriminate them.
John Gacy for instance was captured when he decided to kill a boy that was well loved by his family and well regarded by his peers - which prompted a more thorough investigation by the police.