3 themes of film making

As a film maker, there are a few topics tat i would like to touch on. For the more controversial, documentary kind of work, I'm interested in hearing more about global warming. But not just all the apparently bad things that are happening, but all the good that still exists in the world. I'm sick of hearing how we're all killing this planet without even seeing what there is that's worth saving. Or maybe even some solutions besides buying a hybrid car.
But as far as things that I would like to explore as a filmmaker, I really would like to do a sort of film noir, detective or even gangster sort of movie. I think Mike gave me an idea when he showed me one of his stories. I would like to do something like the Maltese Falcon detective movie, but have two main characters and have them going through issues with one another as they try and solve a case.
I also would like to try my hand at a sort of formalist theme where the main character interacts with another character that only he can see and hear. I'm sure there's some movies like that, but I can only think of Willy Loman in "The Death of a Salesman". I think that it would not only be challenging, but a very interesting way to show internal conflict.