The wise producer first concentrates on the screenplay and makes sure that the draft that will be sent to talent or directors is as strong as it can possibly be. Yes, it will evolve once a director has been hired, the film fully cast and the actors, director of photography, production designer and editor all offer their perspectives.
There is a sense one can develop about when a script really works – this comes with both practice and some success. It’s hard to know what works if you never sell anything. The experienced producer knows that all the hard questions about the story’s plausibility and emotional truthfulness have been asked, and satisfactorily answered, at least to the producer’s satisfaction. If this is not the case, then the script is not ready to go out.
Some writers mistakenly assume that a director and producer will want to change their screenplays, that they should make them longer than usual, put in material that the writer doesn’t care about and thus is willing to sacrifice in some sort of compromise, and take other defensive measures. And indeed, there are directors who maul and defile screenplays, and producers who do the same, although the damage they do can be more budgetary in nature.
The “best foot forward” theory is applicable here. Lead with the strongest version of the script possible, in the hopes that it will attract the right director and cast. Why disguise what is being sold? Loading a script with extraneous material that’s begging to be cut is leading with one’s chin, not with the knockout punch a filmmaker hopes his/her film will be.