Cryptic: Too Many Characters

As I begin my first draft of my new screenplay, I have come across an unexpected development that is really quite a thorny problem.

I have a treatment, which is a five page outline of the complete story, and it works reasonably well as a simple breakdown. Undoubtedly, as the writing develops, and new drafts are written, changes will occur, some major, some minor. For the first draft, however, all I need to do is follow the treatment as written, because if I start to bugger about with it now, and make big changes, it will threaten to divert from my intended path and come to a different conclusion, which will potentially confuse me, and possibly derail the whole film.

But as I wrote the first sequence, I included a character, a person for one of the leads to talk to as he enters the story, someone who wasn't in my (very loosely written) treatment. And the problem is I really like this guy. I have managed to write him as a really interesting character, who I can see would be fun to bring along on the adventure.

This is an issue I find surprising. I don't usually look at my writing as anything other than a way to tell a story. I can't look at it objectively, I tend to know what I'm good at, or feel comfortable at doing, and what level I am capable of achieving. It's weird for me to look at the writing and realise I've just created something really good, beyond what I had planned. He originated through necessity, but by giving him a particular personality, and placing him against the main character in just the right hierarchy, it made him much more fun than I had expected.

So I'm torn. Do I follow the treatment and abandon this new character after page ten, like I'm supposed to? Or do I take risks, and bring this character along on the journey, introducing new dynamics that I haven't accounted for in my original plot?

After some wrestling with the issue, I have decided I will follow the treatment. But as things develop, I will keep an eye out for an opportunity, take note of it, and I may weave the character in during the next draft.