Hello old pal, I disagree the cross took care of the sin nature, the OP describes the mind as looking like the old nature but the old nature is crucified in Christ. It's the mind that must be renewed to the new nature we have in Christ.
It is OK to disagree my brother and you did it in such a Christian and civil way. The truth is a lot of people disagree with me and I love them for it. It says to me that they are INVOLVED in getting out the Word of God and that is what we all should be doing.
To me, it is our sins that are paid for on the cross and are crucified with Christ, NOT our nature to commit sins. We sin because we are sinners and the act of salvation does not stop us from doing what we do best. Salvation is the act of forgiveness but not the process of irradiation or removal of the instrument which causes us to sin and that my brother is that Old Sin Nature.
The "flesh" or as some call it, the
old nature, belongs to us as coming into the world of Adam's race by natural generation; or as some call that "Federal Headship" and "spirit" is the new nature , and it is ours, if born again of the Holy Spirit by coming to Christ.
When we were born again, then there was implanted in us by the Holy Spirit this new nature, which is spirit, and one of the first results of this was the inevitable clashing of this new nature with the old, which you inherited as a child of Adam. Both strive for the mastery, each pulling in a diametrically opposite direction, and until the secret of deliverance from the power of the flesh within is learned, the painful jumble of right and wrong is bound to continue.
In other words we do not have to be controlled by the Old Nature but we will always be subject to it. IMO!
After Paul was saved he admitted in Romans 7:15-18........
"For we know that the law is spiritual: but I am fleshly, sold under sin. For that which I do, I do not own: for not what I will, this I do; but what I hate, this I practise. But if what I do not will, this I practise, I consent to the law that
it is right. Now then
it is no longer I
that do it, but the sin that dwells in me.
For I know that in me, that is, in my flesh, good does not dwell: for to will is there with me, but to do right
I find not. For I do not practise the good that I will; but the evil I do not will, that I do."
Then in vs 22 & 23 he comes to the center of the problem..........
"For I delight in the law of God according to the inward man: but I see another law in my members, warring in opposition to the law of my mind, and
bringing me into captivity to the law of sin which exists in my members."