So here is my understanding of your argument:
God is omniscient. He has a plan for each of our lives, a plan for the entire world. BUT this is not necessarily how things will play out, because we still have free will. If we do give ourselves to Him, we must give up our desire to understand why He chooses certain actions and steps, and recognize it is all part of His grand scheme. This is the right thing to do because in God there is truth, and in God all is right. Day to day sufferings and pleasures are simply steps along the truthful path.
So, allowing polygamy then disallowing polygamy are just steps on this path. When God told Joseph Smith that it is right to have many wives, this was part of God's plan. However, in light of the mounting social pressures put on the church by those who exercised their free will and said "NO POLYGAMY IS WRONG" God was forced to detour. He said "Ok fine, polygamy is wrong" and quickly drew up a new, slightly less efficient version, of His original framework in order to incorporate this new rule.
I believe my view to be much simpler because there is one less force to deal with, God.
In my view, a church was founded to explain things that otherwise were not explainable. It was founded to deal with people's fear that they would join the "wrong church" just as Joseph Smith feared he would. If you join the wrong church, I have been told by pastors and priests, you go to hell. And nobody wants to go to hell right? So this new church, Mormonism, which is the right church, was founded.
Now, if it is a new church, it has to be different than the old churches, or it is the same church. So, Joseph Smith had to set his church apart enough to make it different, but not so much apart that people would have to adopt an entirely new view, and understanding of reality to join. He was smart. He did not want to alienate potential followers. So, he said (among many other things) you Christians are close, but here is where you are wrong. He added polygamy, and a whole bunch of other things, but left the central tenets of Christianity in tact. He gained followers.
The Church grew and grew and I think now is the fastest growing religion in America. It survived, it drew people in, but soon some of those things that set it apart from mainstream Christianity came in to question. Women didn't like having to deal with polygamy, black men wanted equality. So, the church adapted. If it did not adapt, it would die. People would not join a religion that promotes racism and sexism so overtly (I know other religions do this too, and are also guilty of adapting to save themselves). Mormonism changed, not because God said all of a sudden "I decree that there shall be no more polygamy, and yes I suppose black men are equal to white men", but because if it did not change it would die off and be no more.
Darwin's concept of fitness (a very very simple concept) applies to everything, not just finches.
So, this explanation is simpler than the God explanation, because it does not rely on God. It relies solely on the principles Darwin set out hundreds of years ago. It relies only on human nature, and not human nature plus God.
You adapt or you die.
Again, I am always very cautious when I discuss religion because it is very dear to all. Please do not take offense to any of this. This is just what I believe. I respect what you believe, and often have wondered what my life would be like if I was able to trust so much in things I can't perceive. I admire your faith.
