I STAY doubted haha...it is familiar territory for me.
Progress can only be made if someone is brave enough to push the envelope...whether I fail or succeed, I'm sure the data obtained will still prove to be most useful for you young bucks. Just look at it like I'm taking one for the team and the greater good of pimp tightedness.

If there's anyone who can pull this thing off, it's you.
I'm skeptical just because I think you're trying to defy too much of the matrix at one time. Even if this woman will put her ego aside and forsake everything that women are taught they are entitled to in such a situation (child support, ect.), chances are there is going to be some finger-wagging relative or friend that tells her what you are doing is wrong and that you have to cater to her. If that does indeed happen, chances are she will buy it and she will try to reverse the situation. It won't work on you, but it would make your plan go to shit.
However, societal pressure could instead work in your favor. Perhaps she really does not like the idea of being a single mother and the stigma associated with it. It's a fact that single mothers are generally less desirable than women who haven't given birth, and I'm sure she's aware of the fact that this would hinder her possibilities of finding some chump to put in your place. Plus, she's getting older, and I would bet that she will start to become aware of this very fact very soon especially since having a child is one of the last major landmarks of a person's life. If my impression of you is correct, chances are that this girl knows that you are probably the best she will ever do in life in terms of men, and this is obviously advantageous to you.
Ultimately, your success will be determined by how much she likes you and her hunger for power. She could very well lift a very hearty middle finger to the matrix and come over to your team, but I doubt that will ever happen because women love to be pampered. She believes she will own you at some point (because all women believe they will own a man at some point), and she will have more power over you if she legally forces child support and takes custody of your son (almost nothing you can do to prevent this unless you can prove she's mentally unstable or on drugs). Unless she is insanely into you, you may have make a small compromise to get your plan to work, unless perhaps the leverage you have over her is as good as you say (please remind me of her foul play).
At worst, I give you about a 40 percent chance of things working out how you want.