Not to make Matthew Berry feel badly, but perhaps the reason they got the gig was that no one else wanted it. I know a paycheck is a paycheck, but I highly doubt anyone would be excited about writing the third Crocodile Dundee movie.
If that's the case, I'd do what all of the other writers did: come up with some crazy idea (a la Croc in Space) that Hogan and his company would never approve. When Hogan turns it down, you don't have to worry about turning his movie down. I wouldn't be surprised to find out that some of the writing teams spent more time trying to come up with a pitch that wouldn't be used than Berry & Co did to come up with their practice pitch.