out of curiosity, which mythic/pagan origins of the Arthurian cast (and other Welsh or Galfiridian characters) do you take seriously?
Out of the myriad speculations, I think the one I would stick my leg out for is "Guinevere = Findabair". Similarly, "Excalibur = Caladbolg".
In my mind, during the era of Irish migrations into Britain, both Guinevere and Excalibur were "loaned" from Irish Myth (Ulster Cycle), and intermingled with the indigenous Arthur folk stories that existed Pre-Geoffrey of Monmouth that ultimately became too iconic and got spun off into their own unique portrayals, Irish origins forgotten.
Other than that, I also lean a little bit towards "Morgan = Mari-Morgen" theory as parallel to the idea that character Sebile arose from the cultural memories of the Greek Oracles.
