If Jesus’ true identity can be altered, then room is made for another Jesus, with another purpose, and a different Mediatorship, etc.
Scriptural variances do just that in my opinion. While our modern minds seek to know all the technical aspects of everything curious, the bible doesn’t give the blueprint for how the incarnation happened. It simply states that it did. Surely, if we had the capacity to understand the technical aspects of such an occurrence, God wouldn’t be much of an infinite God would he?
So, our goal cannot be one of total comprehension of all aspects of God, which is an impossibility as noted. Believers will be studying and learning from Him throughout all eternity.
Rather, our challenge is to believe what God says. Whether or not we totally understand every minute detail is irrelevant. This was Eve’s problem. She chose not to believe although having the word of God spoken directly to her. We have that same word of God and face that same choice.