One thing likely to go wrong making movie is that it can turn into a money pit. The other danger is that it can be for the writer-director especially a death of a thousand cuts, if a collaborator is not in sync or there is a dispute over the tone and content of a screenplay.
Personally, although I understand this and how common the principle can be, and that I have dodged a few bullets by avoiding or cancelling a project when it was clear that something was afoot, I have spun my wheels for three years imagining what kind of pep talk or statement could have been made earlier on to eliminate even the idea of a power struggle or the project being co-opted by someone else.
The mantra must be “we want the same result or we don’t.” To begin with the end in mind means to see the finished movie in your mind’s eye, even if the idea of a vision sounds pretentious. It is either worth the journey or it isn’t. Your work will be vindicated or it can’t because it is no longer your work. I know that I have no interest in recording improvisations as a replacement for the writing I have tweaked and fine tuned over a long stretch. To open the floodgates on that would be a problem. To allow someone who left the project over a problematic joke to sneak back in under someone else’s say-so and instead have that line or idea cut from the script would be a grating trade-off.
Those who may have an advantage are people who just have outlines and place-holder dialogue they expect to be “improved” by a cast. Such a project would be about building a community and offering a forum for actors to do what they want and to be a leader by association. That is potentially the successful route, and I have seen it happen. Actually knowing how you want your movie to go and fine-tuning your dialogue might set you up for a longer road and more obstacles. The more specific your goal and the more objectives within it, the harder it is to achieve. If your goal is just to have your credit on something, regardless of how much of it came from you, doors open more easily.
Getting people to watch a finished movie, let alone pay to see it, is almost as hard as getting them to read a script. From this point forward I may even complicate it further by novelizing any script I do, or at least making a prose short story that can be absorbed as its own thing and that can be a more digestible introduction to a concept or plot or characters than the simple screenplay which just seems to be asking for financing. But in the end, you don’t want bigger personalities to get into a pissing contest and have more A-type personalities and Beta you to death as each line or scene or shot becomes a hill to die on. Better to say up front that it is okay if someone doesn’t want to do the project and the priority is that they trust the material and yourself otherwise it will be months or years of psychological abuse and only the superficial appearance of accomplishment and a monument to your own lack of influence or debate skill.
Best to keep your team small and focused rather than be drawn and quartered by opposing goals pulling you and the project in every direction. In the past I have let things go from specific to general and the overall impact has been weak. Better to keep the tension in the cut and fuss over the little things that add up. And serve fair notice at the start that this is the way it has to go. Just recording something is not enough.