This is what I tried to explain in my post on Atenism (the religion of Akhenaten) here: [www.grahamhancock.com]
Atenism was an extreme (in my opinion early "Gnostic Christian" form) of the AE belief system. It is Egyptian Gnosticism in its earliest stages.
The Phoenix, (Bennu) bird and Ben-Ben symbolism atop pyramid) is the resurrected/re-born man coming forth from the ashes of his old self, who has undergone the spiritual transmutation and become a (what we now since the Jesus myth call "Christ") enlightened, fully conscious spirit - it's what "coming forth as a lving soul" means. The Book of the Dead is otherwise known as the "Book of Coming Forth by Day" but it also means "Coming Forth into Light" - an entirely different concept to "by day"!!
If you study all the aspects of Osiris (which I'm sure you have) and how he takes his place among the Imperishible Stars, it is the same eternal existence, the same immortality promised by Jesus - those who will know no death, those who will live in God's presence - as the esoteric teachings of the Gnostics (not just the Christian Gnostics but the "pagan" Gnostics before Jesus - therefore, the Christ figure was already alive in the image of Osiris, brought into all the Eyptian writings if only people read them that way. I get so frustrated when people deny it.