Christ has made one new man in him, to try and divide again is to misunderstand the purpose and will of God.
God is not looking to find a way to save men in the sense of trying to find a way where they can be excused. He is trying to find a way to save them of their current corruption and make them like him, in character and Spirit!
Dispensation basically teaches that God has found different 'schemes' to save men. This only reveals man's desire to saved by a scheme, not God's way of salvation.
But we all, with unveiled face, beholding as in a mirror the glory of the Lord, are being transformed into the same image from glory to glory, just as by the Spirit of the Lord. (2 Cor. 3:18)
Earnestly contending for the faith which was once for all delivered unto the saints