Okay, now I really believe that Solas is the elf apostate Solas who stumbled upon the spirit of Fen'Harel just as the young Flemeth stumbled across the spirit of Mythal. What did Flemeth give Hawke to carry to Marethari? An amulet, which summoned her. When questioned, Marethari says it is because of a promise that still has to be kept. I figured that Marethari is bound to Mythal just like Abelas, but I don't think she wears Mythal's vallaslin, does she?
Also, the amulet that changes Cole. Amulets are important to spirit mages in Thedas, it seems.
In any case, I don't believe that Solas is an ancient elf rishing from thousands of years of uthenara, because Leliana says that his village has only been ruined for a few centuries, not thousands of years. I believe that that much of Solas' story is true. He was born a "city" elf apostate who had a talent for Fade magic, and somehow became the earthly bearer of Fen'Harel, either by choice or not. Was the mortal Flemeth given a choice?