Livre d'Or

AIUI one of the arguments in Rabbenu Gershom's cherem was that polygamy worked really badly for even the upright patriarchs, so us normal human beings should definitely not attempt it! But I've only heard about the cherem second-hand, I've not really studied it. I am not really looking for a halachic model of polygamy or concubinage, that doesn't feel at all applicable to me. (I do know someone who considered pilagshut as a workround for the fact that he was a Cohen interested in someone who would be forbidden to marry a Cohen for technical reasons. But neither the relationship nor the halachic investigation came to anything.)