So, I know a fair bit about Mormonism, and one thing that struck me about the religion was how it's very reactionary in the present-day, but was once very progressive. Early on you had things like the beginnings of complex marriage (though confined to the leadership and whoever Joseph Smith wanted to bone that week), a more tolerant outlook on race (abolitionist religion, and at least one Black priest), a much more positive view of women and a greater role of women in the faith (Heavenly Mother), and experiments with socialism (the United Order).
However, Brigham Young basically pissed on all of that, turning the marriage practices into a patriarchal system straight out of the Old Testament, the United Order was phased out, Young banned the Blacks from the priesthood, and women were marginalized more.
So, this isn't an alternate history challenge, but how do you think history might have changed if Mormonism had developed into more of a progressive religion, Mormons even being something like proto-hippies?