I agree with your argument that the ban on polygamy is outdated and reductant. Our sense of morality has evolved. We no longer view same sex relationships as tabu or an affront to the moral fibre of the nation. Why not evolve our thinking about polygamy?

As you clearly state there are more effective laws already on the books to protect women and children.

Personally, I have a hard time keeping one wife happy so I wouldn't be looking for another. However, I may like the idea of her having another husband around. Someone to hang out with. He could help with the chores. We could keep the toilet seat up.