Polishing Up My Thesis that Μαρκίων was Originally a Greek Gentilic Collective Formation

As a means of testing my theory, I have been scouring the Greek books in my possession and the internet to find an example which parallel's Irenaeus's manufacture of Μαρκωσίων (Epiphanius Panarion 1.34.1.1, 34.1.8) from Mark (Μάρκος).  I can't find a single example of this construction.  The facts are nevertheless that this and other examples preserved in the Panarion from the very earliest period of heresy writing demonstrate ίων was originally used as a suffix to create Greek gentilic collective plurals.

Again there can be no doubt that Epiphanius is only following what his manuscript of Irenaeus's lost (at least as a 'stand-alone' lecture) Against the Marcosians called the sect given his use of the term (καλούμενοι):

Against the Marcosians: A certain Marcus, the founder of the so-called Marcosians ... [from] the work written against Marcus himself and his successors by the most holy and blessed Irenaeus (Κατά Μαρκωσίων - Μάρκος δέ τις, ἀφ' οὗπερ οἱ Μαρκώσιοι καλούμενοι ... καὶ ἁγιωτάτου Εἰρηναίου κατ' αὐτοῦ τοῦ Μάρκου καὶ τῶν ἐξ αὐτοῦ ὁρμωμένων πραγματευθεῖσιν)

and then after the citation from Irenaeus's work, Epiphanius against confirms the same name:

But passing his wickedness by as well, and the wickedness of the people who are called Marcosians after him (ἀπ' αὐτοῦ Μαρκωσίων), let us hurry on to the rest, beloved, and in turn discover their roots and counteract the bitterness of their fruit by making public the refutation of it and all of the facts about them.

We know that Irenaeus wrote a treatise 'Against Marcion' referenced in Against Heresies.  How on earth can anyone accept the implausible construction of the 'Marcosians' (Μαρκωσίων) when all other Irenaean gentilic collective plurals drop the equivalent masculine termination in the original name - i.e.'Colorbasians' (= Κολορβασίων or Κολόρβασος - suffix ος + ίων). Similarly we can see 'Epiphanians' (= Ἐπιφανείων or Ἐπιφάνης -ς + ίων), 'Valesians' (Οὐαλησίων or Οὐάλης -ς + ίων) or most significantly against from the Panarion's original source the Outlines of Hegesippus Καρποκρασίων (= Καρποκρᾶς + ίων).

There is simply no debate any longer whether or not the ίων suffix was used to create gentilic collective plurals.  The question simply comes down to whether it is believable that Μαρκίων (= Μάρκος -ος + ίων) was the original - but subsequently abandoned form of 'followers of Mark.'  Μαρκωσίων to me is simply an incredible formation, one which I can't find a single precident anywhere in any Greek text.  Perhaps someone can point it out to me.  The manner of establishing a heretical boogeyman from a gentilic collective plural by back formation is already well established in the writings of the Church Fathers - 'Ebion' (= Ἐβίων) from Ἐβιωναίων (or perhaps the Aramaic original Evionim) and perhaps Elxai (Ἠλξαῖον) the 'false prophet' from the Ἐλκεσαίων (although a borrowing directly from Aramaic is more likely here).