One of the things I enjoy about our conversation is how your mind pivots to point in unexpected directions. Polygomy was not on my radar!
Your summary of the relevant history is on target. I did not know the particulars of medieval Jewish regulations, but I am familiar with the Hebrew Bible's approach to the subject. "Regulation" captures it nicely. For the most part, starting with the Seventh Commandment and running through the passages you mention, regulation seems to have been designed to protect the woman or women involved. Perhaps the same was true of the medieval legislation, or was it developed primarily to reduce the chance of legal or mob persecution?
Getting back to the Bible, I have to wonder how many men in ancient Israel could afford the practice. Was monogomy more nearly the norm than polygomy? In either case, though, the commandment against adultery applied, thus restricting men's conduct more than was normal in the ancient world.
As I've noted in earlier entries, I think God starts where we are and tries to move us as far as possible toward his ideal. His work is formation work. As a result, I need not agree that "God favors polygamy." In fact, I think the practice belongs to an earlier era. I do believe, though, that God favors fidelity in marriage, both for the kinds of practical reasons either of us might list and because it's good training for a man or woman who would become faithful to God.
Both of us, I think, sometimes engage in a bit of hyperbole. For example, you write that our society practices serial monogamy. I would argue that a percentage of our society does so. Observation leads me to add, though, that some individuals seem never to practice monogomy of any kind. Remarkably, some portion of the population does. Monogomy, therefore, is possible, though individuals may (and do) find it very difficult for any number of reasons.
If monogomy is so hard, and in some ways runs counter to our biology, why would God require it? We've already alluded to the benefits to society and the possible benefits to women, at least in ancient times. I suggest the deeper reasons are that it is good for us in general and good for our relationship with God.
Growing in the ability to give another person exclusive devotion strengthens character, develops charity, and encourages a growing acknowledgment of one's own rough spots and foibles. All such developments are good for us.
Furthermore, such developments may lead us to better comprehend and accept the faithfulness of God and the challenge we present his faithfulness. That's good for us, too. Far from our being "a great catch," we come to see that the wonder is that God pursues and stays with us at all!