I think you're the only person I've ever seen who is able to separate those things from "age gap", anon. So, yeah, for you it's a total non-issue. But for the American culture at large, there's almost a built-in squick-factor (in some cases, even when the age gap is minimal, such as teacher/student relationships; watch any report from the news on one of those coming to light and there's implied if not stated disgust at the age difference, even when it's something like a 17-year-old male student and a 25-year-old female teacher). It's neat you can make the distinction, but the viewers who do object to Jack x Ashi because of the age gap don't see it.
Personally, I don't see how Jack can't have power of Ashi because of his extra years of experience. Ashi herself is further disadvantaged because her upbringing, regardless of her physical age, has left her mentally stunted. I don't think Jack would intentionally take advantage of her, which is another reason why I personally don't think they'll hook up. Now that he's getting the measure of Ashi's rather one-track mind, he'd probably want to try and undo some of the damage she has that he blames himself for, but sexual healing is not covered by that metaphorical insurance.