Marriage nowadays seems to have devolved. There was a time it was it was a strong institution in people's souls. Nowadays it is all about business. A way for the woman to make money, for a long as it is convenient. So what I think is the approach of the concubine פילגש makes the most sense. Since we find that Caleb ben Yefuna had a few, as we see on Chronicles chapter 2 verses from around 46.
And he was the only person in Torah of whom it is stated וימלא אחרי השם He went totally after God. So this is not a sin.
At any rate, this is the Raavad, Ramban, and other Rishonim besides the Rambam.
[Women nowadays -tend to think of themselves as goddesses.-which they are not.]
