Hmm, nice post.
I think that a balance is required of the two, there will be aspects of the relationship where the man will be in charge, and there will be aspects where the woman will take charge. There's nothing wrong with that, a balance is needed, and most of the time it naturally occurs, and allows the relationship to be healthy.
As far as the phrase "wearing the pants" goes, I don't think there's anything wrong with the men wearing the pants in the relationship. The phrase comes from the traditional view of men going to earn the money and the women staying at home and taking care of the kids. Although the times have changed, human nature hasn't, I think most women like having a man they can depend on, someone who will take charge and be able to provide for her and the family. Its not that the woman can't do that herself, but its just a natural tendency that most women, who are secure about their relationship, and their status in the relationship, want. Of course this doesn't apply to all women, but I think its a generalization we can make. Likewise, most men are happy knowing they can provide for their families and be able to support their significant other. Again, something that is inherent in the male gender.
Plus in most cases, men are happier wearing the pants, and women are happier letting the men think they are wearing the pants ... you know sufficing both the ego and the need to take control. 😆
As far as your example goes, of the woman breaking off the relationship, well I don't think it has anything to do with "wearing the pants" ... its a matter of a relationship breaking, and those usually are one-sided. It won't be fair to either if she continues the relationship just because she doesn't want to hurt him. She shouldn't have to put herself through that and the guy deserves much better than that. But that's a different issue, IMO.