No, I'm most interested in choices. We make conditioned choices. The need to care for someone, the need to pay the bills, which opportunities we have (job offers, for example). Those are not equal for anyone.

From what I see, in religion, the conditioned choice is basically that you are allowed to work outside the house as long as you have taken care first of the caring of children and elders and house chores.

Compare that to the expectation to cover the bills, but knowing that if you "drop" the domestic chores and the care of the elders, you can rely on the women in your family to pick up the burden from you. Then you can focus on your career (but you'll find it more difficult to find time for the caring and the house).

"How do you know who the father is?" --> Now we have a paternity test if biology is that important. Therefore, technology would have rendered the restriction obsolete. But let's be honest here, it is not about just that and we both know it. Polygamy allows for a man (who can afford it, if I remembered well) to have the full attention of several wives while he divides equally. So if he has two wives, then he would have 100% of their attention to a total of 200% of attention and give them 50% of his attention to each. That means that he is getting 4 times as much attention as the wives are receiving. Not very equal, is it? Plus, books about polygamy like Kamasutra encouraged to make the wives "compete" for the husband to his benefit...

Now, it would be different if we are talking about polyamory, where the two wives happen to be bisexual and enjoy each other company. But I'm not sure about Islam's stance on homosexuality. I do know that some countries ban it and prosecute it.

Technically, polyandry could be the same. You can reach agreements and do a paternity test. Not just that, there is another answer to your question about paternity: The one who raise the child. That is the father. And if all of them participate, the child would have more than one father. The question is, do you think that Muhammad, who apparently adopted a son, was his father? If the answer is yes, then it follows that biology is not that important and my previous answer would have been valid if you considered equality important. Doesn't matter who impregnated the woman among her husbands, what matters is who raised the child.

Either google is wrong (could be) or some of those late wives started being his slaves. I've taken interest in that part because of this:

"Slave women were required mainly as concubines and domestic workers. A Muslim slaveholder was entitled by law to the sexual enjoyment of his slave women. While free women might own male slaves, they had no such right."

Those women couldn't refuse him. And he could have had sex while married to his first wife. But his wife, couldn't have done the same.

There was unequal treatment of men and women in Islam. That doesn't mean it can't change in the future. Religions do change. But the first step is to admit that back in the day, it wasn't the case.

All the achievements of those women don't deny the inequality I'm pointing out. Those women weren't allowed to have several husbands, and some of them weren't allowed to say no to sex. Something in this line:

"their spouses or what their right hands possess"

Not equal, not free.

I'm aware that Islam encourages the reading of Couran* (Unsure about spelling in english) and that there are several interpretations. But chances are that Muhammad marriages were influenced by the culture at the time. So should you take that as the limits of equality in Islam feminism? Or maybe a Muhammad today would have thought differently? I don't know, but I can see how some things are still unequal.

As you see, we have both a biological and a philosophical answer to your paternity question. No reason for no-polyandry beyond culture.