You're a real fucking poet, Sydney.
There's a lot of theories, but I'm of the opinion that Dougie Jones would have the best chance of winning. He is Cooper's good heart and childlike wonder distilled into a person, without any of the anger, arrogance, or vengefulness that Cooper occasionally displayed. Remember the scene in season 1 where Cooper has has Hawk and Harry help him use the "Tibetan method" to find clues - basically throwing rocks at bottles while he thinks about people? That's an example of Cooper trying to be like Dougie (even though Dougie didn't exist yet). Dougie is like a divining rod for fate and the forces that control the universe. So if any human from the Twin Peaks universe has a chance at beating Muad'Dib, it's Dougie. But if Dougie won, it would only be because that's what the universe wants to happen - Dougie has no will of his own. He's just vibing, going along with the flow, as a conduit for the forces of good. Tulpa Cooper is the opposite of this - he's all the bad things from Cooper distilled into a person. All the bad impulses without any of the restraint. He's more sophisticated than Dougie - smarter, driven, capable, forcing things to follow his will. But he's at odds with the universe, and for that reason is always fated to fail.
That's why, to me, Cooper is such a compelling character. He has the forces of good and evil within him, but is aware of himself and those forces. By acknowledging them, he is able to act thoughtfully and choose which side of himself he'll allow to win. And he consistently chooses the side of good, even when it hurts him or forces him to forgo something he wants. This stands in stark contrast with many of the other characters, most notably Laura Palmer, who is an excellent foil for Cooper. She has immense good and evil within her, but he doesn't know herself and consistently indulges those evil instincts. Which allows her to fall under Bob's sway. That's also why she's such a prize to an entity like Bob - she has so much good in her, which makes her suffering and self loathing when she's evil that much greater. To Bob, that's the best form of sustenance (i.e., garmonbozia).