Saying "One Flesh" does not rule out Polygamy.

I went pretty in depth on Anti-Polygamy arguments awhile ago.
https://solascripturachristianliberty.blogspot.com/2018/08/just-accept-that-bible-doesnt-condemn.html

What really annoys me though is how often I see people argue simply that a Man and Woman becoming "One Flesh" when they are united (Genesis 2:24, Matthew 19:5-6, Mark 10:8 and Ephesians 5:31) in marriage somehow proves only Monogamy is valid.  It boggles my mind how people think this statement rules out Polygamy. 

They are operating under an assumption that you can only legitimately become "One Flesh" with one other person, even though nothing in Scripture says that.

In fact the New Testament actually teaches that the Entire Church is supposed to be One Flesh, we are The Body of Christ because we are the Bride of Christ and thus made One Flesh with Christ.

Paul even directly connects these ideas in 1 Corinthians 6:15-16, where he argues that the reason Believers shouldn't have sex with prostitutes is because the members of Christ shouldn't become "One Flesh" with the Members of a Harlot.

People keep misunderstanding what Jesus said about marriage and the Resurrection in his response to the Sadducees in Matthew 22, he's not saying there will be no more sex or marriage, that would undermine it being a return to Genesis 2.  When that time comes there will be only one Marriage that matters, we will all be married to each other in Christ.

So yes I am arguing that in a sense The Church should view itself as a giant Polyamorous group marriage.

The context of what Jesus said when He made the One Flesh reference was about condemning divorce (meaning He was willing to directly condemn something Moses allowed if He wanted to) and so would include a Husband with two wives wanting to divorce one because he decided to be Monogamous, if the relationships were consummated he was "one flesh" with each of them.