Qcmbr,
Why differentiate between angels ( messengers ) and human spirits? If angels can mate with humans stands to reason they are humans. In fact why make man in the image of god, make man genetically compatible with god ( hence Jesus could be conceived ) and then promise us that we could be gods...unless that's the plan?
I believe angels have a different makeup than human spirits. I do not believe angels would have to be human in the first place to mate with women.