And I've explained previously why women are "cool with it". Because 9 times out of 10, they've got zero choice in the matter, and have been indoctrinated into believing that they're essentially second class. If someone is in a polyamourous relationship, or in a polygamous marriage with multiple spouses in a FREE society where it's not enforced by ignorance stemming from religion, then it's totally ok. And I seriously doubt that you've talked to any women from cultures that have cultural, religion based polygamy, since in those cultures no woman would speak to a man without either her husband or father giving the ok and that's not likely to happen. In any case, I'm not here to dispel anyone's ignorance but if you're interested in the topic I suggest you educate yourself with proper secular sources.
My point stands though, this game doesn't in my opinion need any storyline based in cultural or religious polygamy to justify the MC' relationships with multiple women, and at this stage in development to introduce a story like that into the game would just feel awkward and forced.