Outside the Animus
There isn't a whole lot of time spent in the "real world" of Desmond Miles in the first game, but hopefully that's something that the movie will expand on a bit. Having scenes bounce back and forth between the third crusade and the near future with two interconnected stories would certainly set the film apart from it's theatrical competition when it does see the light of day.
7. Warren Viddic - Helmut Bakaitis
The man in charge of using Desmond Miles to find out what Altair discovered in 1191, Vidic is a cold hearted, ruthless man on a mission for information who doesn't care who gets hurt along the way. During moments when Desmond is unplugged from the Animus, Vidic doesn't even try to conceal that he doesn't plan to keep him around longer than necessary. For cold and calculating, no one else has quite the dry flair as Helmut Bakaitis. Although he's only notable for his brief appearance as The Architect in the Matrix sequels, he nailed the part so perfectly that he's remained in the cultural memory of nerds even though many have tried to forget everything about those movies. Bakaitis would bring the appropriate level of dispassionate ambition to Vidic, and it'd be a nerdy delight to see him in another block buster sci-fi flick.
8. Lucy Stillman - Kristen Bell
Vidic's assistant who handles the technical work of connecting Desmond into his DNA memories, Lucy Stillman is more than she initially appears to be. While initially being the one sympathetic person that Desmond can talk to when he's not reliving the life of his forebear, as the plot moves forward it eventually becomes apparent that Lucy can offer much more help than merely a friendly ear. The first time I played Assassin's Creed I found myself thinking "if that movie version ever gets off the ground they should totally get Kristen Bell to play Lucy" eventually I realized there's a good reason that actor was the first to jump to mind. It's because Bell is already playing the role as voice actor. With that in mind, it seems like a no-brainer for Ubisoft to bring her on board for the movie.