I think Bentley Bear would make a good mascot, both because he's a classic character, and because the character is gameplay-agnostic. You could transport Bentley and the other characters into different scenarios and different situations without too much difficulty: Berthilda The Witch and her magically-animated minions stir up trouble somewhere, and here comes Bentley Bear and his magic hat to save the day. (Like Mr. Do, if Universal still existed and needed a mascot)
And even if he's not that well-known right now, that's no problem that a really good and popular game couldn't solve. (The trick is not to half-ass it, it has to be a genuinely good game)