Yes I was aware he was in Da Vinci Code with McKellan, but they never had any scenes together, so I wasn't sure if they actually "worked together."
I don't see the Spidey/verse fitting into this particular storyline, and I also don't think it would have the "wow" factor Olson and Bettany have mentioned (unless it's Tobey Maguire). IMO, among the Marvel characters in current cinematic existence, I think the only "wow" factor options would be Magneto, Jackman as Wolverine, Professor X, or Tobey Maguire's Spiderman.
Reed Richard's/Dr. Doom is certainly possible. But they're introduction may not really need a "Luke Skywalker" moment.
Of course it's possible Olson is exaggerating the "Luke Skywalker" type of moment in the series and it will indeed be someone you listed. But it's been reported McKellan and Fassbender both were approached for the series, so Fassbender is where I'm hedging my bets. It also fits with the family theme going on in the series.