There is the concrete possibility that the Jesus passage in Slavonic Josephus could reflect the knowledge of the Gospel I am talking about that could precede Mark.
1. At that time also a man came forward,—if even it is fitting to call him a man [simply]. 2. His nature as well as his form were a man's; but his showing forth was more than [that] of a man. 3. His works, that is to say, were godly, and he wrought wonder-deeds amazing and full of power. 4. Therefore it is not possible for me to call him a man [simply]. 5. But again, looking at the existence he shared with all, I would also not call him an angel.
6. And all that he wrought through some kind of invisible power, he wrought by word and command.
7. Some said of him, that our first Lawgiver has risen from the dead and shows forth many cures and arts. 8. But others supposed [less definitely] that he is sent by God.
9. Now he opposed himself in much to the Law and did not observe the Sabbath according to ancestral custom. 10. Yet, on the other hand, he did nothing reprehensible nor any crime; but by word solely he effected everything.
11. And many from the folk followed him and received his teachings. 12. And many souls became wavering, supposing that thereby the Jewish tribes would set themselves free from the Roman hands.
13. Now it was his custom often to stop on the Mount of Olives facing the city. 14. And there also he avouched his cures p. 107 to the people. 15. And there gathered themselves to him of servants (Knechten) a hundred and fifty, but of the folk a multitude.
16. But when they saw his power, that he accomplished everything that he would by word, they urged him that he should enter the city and cut down the Roman soldiers and Pilate and rule over us. 17. But that one scorned it.
18. And thereafter, when knowledge of it came to the Jewish leaders, they gathered together with the High-priest and spake: "We are powerless and weak to withstand the Romans. 19. But as withal the bow is bent, we will go and tell Pilate what we have heard, and we will be without distress, lest if he hear it from others, we be robbed of our substance and ourselves be put to the sword and our children ruined." 20. And they went and told it to Pilate.
21. And he sent and had many of the people cut down. 22. And he had that wonder-doer brought up. And when he had instituted a trial concerning him, he perceived that he is a doer of good, but not an evildoer, nor a revolutionary, nor one who aimed at power, and set him free. 23. He had, you should know, healed his dying wife.
24. And he went to his accustomed place and wrought his accustomed works. 25. And as again more folk gathered themselves together round him, then did he win glory through his works more than all.
26. The teachers of the Law were [therefore] envenomed with envy and gave thirty talents to Pilate, in order that he should put him to death. 27. And he, after he had taken [the money], gave them consent that they should themselves carry out their purpose.
28. And they took him and crucified him according to the ancestral law
http://www.sacred-texts.com/chr/gno/gjb/gjb-3.htm
The Jesus who is considered by the Jews as their presumed Messiah and therefore crucified seems to be the same gnostic Jesus Son of Father of which "Barabbas" is probably a mere parody.
Note the absence of Judas in the role of the betrayer: this because Judas served only to point out, against Marcion, that Jesus is "of the tribe of Judah", i.e. really the Jewish Messiah. So who takes the 30 denarii is Pilate and not Judah.
Pilate is so the betrayer in the Earliest Gospel: he captures Jesus and gives him to the Jews. So the gentile Christians who judaize (betraying Paul) are really repeating the same betrayal of this Earliest Gospel Pilate: they are crucifying
again Jesus. So this allegorizes what Paul said: the circumcision implies that the crucifixion is vain.
So the death of Jesus is vain in the Earliest Gospel: afterall, who dies is only the man Jesus. Not the divine Christ. 
