Nothing's Impossible

Why not polygamy?

Mandy Patinkin would have had one woman to take care of his home and children and one to discuss the Torah. Barbra would have had someone to take care of the household duties she had not talent for or interest in. Amy Irving would have had two scholars to tend to (more people to care for being a good thing for people-pleasers). They all cared for one another. They respected one another (except for Mandy's chauvinism issues). If nothing is impossible (a recurring theme of the movie), why not?