if the Cubs draft him by definition he isn't even the best player in the draft
Although this may be true with respect to Appel, I disagree with the presumption that the #2 pick "by definition" isn't the best player in the draft. First, there may not be a consensus best player in a given draft. One team's #1 is another's #2. For example, I would assume there was a split in 2001 when Mauer was #1 and Prior was #2. Also, signability is a factor. I agree that given that he's a college senior, signability may not be a huge factor with respect to Appel this year, but in at least some years, it has to be a factor that might cause the team with the first pick to not take who they believe to be the best player in the draft.
All that being said, I like the idea of Appel because it's reasonable to assume he could be major league ready in a hurry. Certainly, you'd have to think he'd have a good chance of being able to be in the majors by 2015.