It's pretty hard to answer a question about polygamy when its not the intention of that illustration. If you want an answer about polygamy itself, it is more of a product of the impact of tribal wars in the 2nd millenium BC. Lots of men were lost to war. You can see the impact on marriage. It makes polygamy fall into the same category as slavery in the Law. It wasn't the ideal, but was unavoidable (economies scraping the bottom) yet the rules and terms in the Law were so favorable to what modern times would call the victim (the 2nd or 3rd wife or the slave) that those people were better off staying than going.
In 1st century Judaism there were two main rabbis teaching about divorce, but both were thinking in terms of monogamy. The 'permissive' view was that of Shammai while the strict view, closer to Jesus, was Hillel's. What Paul says in Rom 7 reflects Hillel and Jesus. Hillel was very practical and direct, but I am not aware of him building upon Gen 2 or at least not putting that in writing as did Christ.
The earliest of the Gospels, Mark, which went to more Roman audiences, was phrased to reflect that women as well as men could initiate a divorce. The allowed condition was the same: only for infidelity (even that which was found after the fact of their marriage from before it). Matthew (circulated mostly in Judea) makes it sound like only men could initiate. So in Judaism at the time, that seems to have been the case. I Cor 7 shows women initiating, and this is expressed to the wild atmosphere of Corinth.
All of this should come after our understanding that the provision in the Law for a certificate for a woman divorced was a huge advance on anything in surrounding culture.
I therefore doubt if Paul meant to convey a suppression of women in Rom 7. It simply reflects the Judaism he grew up in and often had to address. To make a point to those in Judaism concerned about the status of the Law in his teaching, Paul explained it in the terms they were familiar with. A person "dies" while believing the Gospel (or rather, their "mate"--the Law--dies), so they are not obligated to it as in the past; they have a new husband. Those raised in Judaism should not feel like they are 'cheating' on the Law. There is a new romance.
