Giuseppe,
I would tend to accept that Simon of Cyre'ne was in the base document used by Mark and Matthew. There is no mention of Simon in John, and the passage (23:26-32) is not attested in Marcion. Tertullian says much of 23:33-43 was "cut/erased" and Epiphanius reports from his sources that Marcion read
'And when they were come unto a place called Place of a Skull they crucified him and parted his garments, and the sun was darkened.'
Καὶ ἐλθόντες εἰς τόπον λεγόμενον Κρανίου τόπος ἐσταύρωσαν αὐτὸν καὶ διεμερίσαντο τὰ ἱμάτια αὐτοῦ καὶ ἐσκοτίσθη ὁ ἥλιος
Not even the two criminals were mentioned. So much for Klinghardt's Marcionite names.
Further, Matthew 27:38 (Mark 15:27) and 27:44 (Mark 15:32 b) look like a stand alone verses that do not interact with the story. The same can be said, even more so with John 19:18 b, where they are not even called robbers. Luke 23:39-43 is clearly a secondary development filling out questions asked about what the criminals said -- typical apocrypha reasons. For the two Lesthai, again the Matthew and Mark common source is where we probably have to look for their symbolic meaning.
As for Simon, there is some real evidence to support you hunch, at least that he is post-Marcionite in the fourth Gospel. John again (like so many other theological points) takes issue with Matthew's account. While Matthew (and Mark) says that Simon was compelled to carry the cross, John 19:17 directly refutes that, saying 'Jesus ... went out, bearing his own cross.' John betrays knowledge of Matthew's version, and rejects it, and like Marcion (although John is clearly not a Marcionite, rather he belongs a different heretical sect) his Christ needs no helpers. This confirms to me there is a proto-orthodox symbolism in Simon.
And we have to look for the symbolic understanding of Simon of Cyre'ne within the proto-Orthodox texts of Mark and Matthew, just as we must for the . (Luke IMO is entirely secondary here, using Matthew as his source.) Mark's comment about Simon being the father of Alexander and Rufus is secondary legend, but apocrypha about them might shed some light (thinking aloud here, have not investigated).
“’That was excellently observed’, say I, when I read a passage in an author, where his opinion agrees with mine. When we differ, there I pronounce him to be mistaken.” - Jonathan Swift