Why one earth would God want to show himself to Smith, who was hardly a saint by any standards?
On the other hand, what better person to come to? You have to remember that Smith was something like fourteen at the time. Reality is a fascinating thing when viewed through the eyes of a child.
In regards to the OP, I believe in the Hindu concept of the Avatara, which means, "descent into flesh". In this context alone, "god" can indeed be a physical being. No, that physical being itself is not the totality of what "god" is, but it does represent the fullest aspect that can be contained within the human form. Truthfully speaking, people have a tendency to consider the "mortal" body of the Avatara as the sum total of the Avatara while ignoring the reality that said being represents and is directly supported by. They are one and the same and there is a direct link, at all times, between the two. But heck, what would I know that others do not. Hehe.
Aside from this Kathryn is correct. "God" or "All That Is" holds an "idea shape" projected into the world of the human animal to which the human animal can relate. In no way does this limit "god", by assuming a form, as that form is precisely whatever people understand it to be.
GIven that I have met my own version of this "idea shape" it is not unreasonable to claim to know a little bit about the discussion at hand. At least I have my unique experience where others merely have their esteemed conjecture. It is my perception that the naysayers in this thread do not have the slightest idea what they are talking about and simply demonstrate the limitations of their own preconceptions. That is a great pity, but it is also reality.