Taking these facts into a doctrinal stance, here are some things that might be interesting to discuss and think about.
Why is it that Mormons, in particular, believe that the only way God the Father could bestow powers upon Jesus, or anyone else for that matter, would have to be done through physically "siring" him?
I think this is better said why did 19th century Mormons teach this and why did some 20th century GAs continue to do so? I do not know why. I think this has fallen out of favor.
Why could Jesus not be the physical son of Joseph and Mary? Joseph and Mary WERE married when Mary was pregnant with Jesus. The betrothal was the first state of marriage. The reason that Joseph had the option of Mary being "put away" is because she conceived during an "off season" time for a kingly line. Both Mary and Joseph were instructed by angels that the child Mary was carrying was the Messiah, or the rightful king of kings.
Sure. Some early Christians believe Jesus was an ordinary man who was adopted to be the Son of God at the time of his baptism. Though this was was later considered a heresy and stamped out.
I