Tired at the moment, so I don't have much to work with right now. So far, here's what I have for a PF version of Väinämöinen:
A Words of Power bard/Loremaster PrC with 10 mythic tiers and Divine Source. Bard gives him his longsword proficiency, the ability to be a decent melee fighter, and his legendary performance. 10 mythic tiers and Divine source give him some of his stronger abilities without having to multiclass, such as immortality, Artifice domain SLAs, and so on. Loremaster gives him full spellcasting progression, lore, greater lore, and secrets.
I don't think he's very high-level compared to a 20th-level character, but his mythic tier is probably high. I think he'd be an Archmage, maybe Dual Pathed into Champion. He'd probably have Display of Intelligence.
From what I've seen, he used a little conjuration, illusion, divination, and abjuration, plus a lot of transmutation and moderate amounts of necromancy, more in the separation of body and soul aspect than the undead aspect. He didn't use evocation or enchantment, relying purely on his legendary performance to convince people.
Anything else? Can't think of a specific build, but he was skilled in melee and probably set in E8.