Now I understand your points better. Speaking on the basis of intimate bond, poly setting may not encourage a stronger bond as much as mono. And I said "may not" because the individual contribution matters a lot.
Poly relationship is more about the individuals freedom (especially sexual freedom). Although, some poly families are doing great sharing joint custody with all partners involved, negligence, oppression and jealousy which are some of the problems in mono settings are at minimal.
And like you said, we are yet to see the effects poly has in relationships in the long term. However, we can already see that women sacrifice less in poly relationships than they do in mono relationships which is why women are adopting more poly settings.
As for the men's involvement in their children's lives, I can see that there's no significant difference in the fathers commitment in both poly and mono. So it all goes down the who the man is. If the man is the commitment type, then he will be involved in his kids life whether he's in mono or poly relationship.
You may argue that the law ensure that men stay involved in the child's life in mono marriages but we both know the same goes to poly marriages. In other words mono fathers are no better than poly fathers. The individual man is the factor player in all relationships.
My contentions about mono is that it favovors men's sexuality over women. Whereas poly favors both men and women's sexuality equally. Women have more autonomy over their body, their professional and romantic life in poly settings than they do in mono. And this is what should be important to us (both genders) because it fosters equality and that is where the future is headed.
Women's sexualitu is just as important as that of men. And like you invariably pointed out, somen women in poly relationships are sexually starved just like some women in mono relationships too. But the difference is the woman in poly relationship has all rights to seek sex outside her partner (i.e depending on their arrangement) without risking her self image, while the woman in mono cannot.
But in the end, we are all entitled to choose a relationship style that suits us. I believe poly is here to stay as much as mono is.