Clarifying carnal: I believe there is a difference between carnal nature and sinful nature. As far as definitions go, I believe carnal is best understood as the uncorrupted nature of Adam and Eve before the fall, and that of Jesus nature being uncorrupted by sin, although we all have a carnal nature. I believe the carnal nature includes hunger, thirst, sexual desire, emotions, and all things that we are born with that were made to glorify God in the appropriate context. All those same things when driven by sinful nature (now born with since Adam) and desire can be twisted away from their initial purpose. If anyone has a different name for what I just described, let me know.
Believing God encompasses three different persons, I then understand that the person of Christ came in his divinity into human flesh, where both carnal and divine natures existed simultaneously. Why is it this way? Man exists to glorify God, but is unable due to our inherited sinful nature. In Christ's divine and human perfection, fulfilling our purpose, God is glorified perfectly and mere man doesn't take the glory. It has been God's will to reign with us as our head since the beginning, and sending a created being to do the work wouldn't solve our need to relate to God on the ultimate level as Lord and savior, in righteousness, displayed faithfully in His eternal being.