You're just channeling the gnostic dualism that views everything as being determined by nature. The spirit man can't sin, but the old man can. Guess what? This dissociative separation only exists in the mind. Man is a whole comprised of old man and new spirit, and GOD holds the whole man accountable for what he does with the body.
The gnostics did not believe this. They believed that they were saved by their spiritual nature, just as you do; and that the conduct of the body was irrelevant to salvation, just as you do (and even said so in your post).
Budman: how we live our lives has no bearing on whether or not we keep our salvation ... We are holy, righteous, and sinless because that is what He is, and what His nature in us proclaims
Gnostics (per Irenaeus): [the gnostics] hold that they shall be entirely and undoubtedly saved, not by means of conduct, but because they are spiritual by nature... it is impossible that spiritual substance (by which they mean themselves) should ever come under the power of corruption [of sin], whatever the sort of actions in which they indulged.