The earliest tradition is NOT the Ebionites. You made that up.
I think the methodology used to make the Ebionites early is the Criteria of Question Begging: they are thought to be 'low christology' therefore they must be early, and because they are early it is 'evidence' the early christology was 'low' QED.
There is no claim by Apologetics that the Ebionites were the earliest Christians and the Ebionites are mentioned in writings attributed to supposed 2nd century writers or later.
It appears the Ebionites use gMatthew:
"And they (the Ebionites) receive the Gospel according to Matthew. For this they too, like the followers of Cerinthus and Merinthus, use to the exclusion of others. "
http://www.earlychristianwritings.com/text/gospelebionites.html
The earliest known source to mention the Ebionites was "Against Heresies" attributed to Irenaeus c 180 CE and the author claimed Jesus, the Son of God, born of a Ghost was crucified c 50 CE or when he was an OLD MAN.
Obviously this is evidence of an oral tradition which could only survive because it was
true, based on the Criteria of Embarrassment...
The Jesus cult of Christians started WITHOUT an historical Jesus just like the Jewish religion started without an historical God or the same way Marcionism started WITHOUT a real Phantom.
Well of course there was an historical Yahweh. It's absurd to think there was a religious cult that wasn't based on true events and real people.
It makes no sense that the Jesus cult started with known lies.
If people of the Roman Empire including Jews actually knew Jesus and that he was crucified as a criminal then it is virtually impossible that such a character would have been worshiped as a God and claimed to be the Messiah AFTER he was dead.
The total absence of a non-messianic Jesus would seem to indicate that the character of Jesus was conceived of as a savior from the beginning as depicted in even earlier literature.
Jews do not worship men as Gods and Romans do NOT worship Jewish criminals as Divine creatures.
How the alleged 'disciples' from the backwaters (as depicted in 2nd century tales) could come up with the ideas attributed to them seems like quite a huge hole in the HJ hypothesis. These are not theologians or philosophers.
The personal savior cult seems more appropriate to the Greek speaking world outside Judea.
Paul, a Pharisee, would have been regarded as a suicidal IDIOT if he actually attempted to evangelize the Roman Empire claiming that a KNOWN executed Jewish criminal was Lord, the Son of God, the Savior and that every knee should bow to him even the Emperors of Rome.
The Pauline Corpus only makes sense if there was NO KNOWN historical Jesus.
You put your finger on a very sore point for the HJ hypothesis - when Paul asks people to check out his story he asks they go to scriptures to verify his facts - which dovetails nicely with his claim to know Jesus only through visions and interpreting scripture.
If there was ever a real Jesus, surely Paul would have to make arguments with people who knew Jesus as a man but not an angel, god, or whatever divine being.
The utter absence of an HJ heresy in the 1st and 2nd century is convincing evidence that no one had any idea of Jesus as a real man during that time period.
There is NO history of Jews who worshiped Men as Gods.
Apparently some ignorant Galilean peasants dreamed up the idea themselves with no outside influence - and amazingly came up with a savior cult just like the surrounding regions. An amazing coincidence of history!
The Jesus cult of Christian started WITHOUT an historical Jesus sometime in the 2nd century or later.
At least this is where all the literature is found. And if we decide to stick with an evidence based theory that is where we will have to locate christian origins.
Up to the 5th century even Jesus cult Christians claimed Jesus was NOT born which is evidence that there was NEVER any established evidence of an historical Jesus.
It does seem the cults that became blended into what we know as christianity were wildly divergent, which makes sense if it was something of a syncretic religion arising out of a widespread craze for interpreting the Septuagint and other literature and generating new communities and interpretations over many places over a long period of time.
It's interesting that when the gospel tales finally came to Judea they had to be interpreted from the Greek, as there was no local Jesus tradition.
The Jesus cult did NOT even need and historical Jesus--they needed a Myth--their Jesus was the Son of God who came down from heaven.
This does seem to be the earliest Jesus found in literature.
The mere mortal Jesus doesn't crop up until the 18th century AD.