You wrote:
“A Jew converting to Christianity would have to agree that his beloved ancestors are in hell but that he or she hopes to do better.”
Uh, no.
“Such a person would obviously not be worthy of salvation.”
Anyone who comes to Christ can be made worthy by Him.
“Until Christian doctrine on salvation only by faith in Jesus changes, this impediment is insuperable.”
We don’t believe in sola fide. We do believe in the necessity of faith in Christ, but we don’t (and we can’t and wouldn’t) condemn to hell those who knew no better through no fault of their own.
Would you say that Gandhi and Einstein “knew no better through no fault of their own” in not believing in the divinity of Jesus?
I think that is playing with words to evade an inconvenient issue of religious doctrine.
At the time of redemption, all, including devout Christians, will come to understand the true meaning of the unity of God.
Hum, well, isnt condemning anyone to hell not your prerogative anyway?