Firstly, MOST of the schools I have interviewed at accept at least 40, if not 50+% of their interviewed applicants (examples: Northwestern, Case, Pitt, both NJMS schools, NYU, etc.). They only enroll 1/4 to 1/8 of the interviewees, but that's not the relevant statistic. If my app is good enough to get a september/october interview, then I'm content to let my app do the heavy lifting the rest of the way.
Second, it seems to me that most interviews these days are really low impact. Maybe in the past they were seriously evaluative, but if you only get a handful of basic questions about your activities followed by 'why do you want to be a doctor?' and 'why do you want to go here?', where is there room to hit your home run? I think interviews are overly emphasized because once you get to them, they are the only remaining component of your application that is yet to be determined, so they are the only thing left to do that matters. They are never the most important thing.
Thirdly, I'm not saying that you should go in there and say nothing. Give honest, complete, and simple answers. If you get a chance, talk about music or sports, and you'll come across as far more human and balanced. If your app has a flaw, use the opportunity to put it in a better light. That's it. This strategy you're discussing that revolves around determining exactly what they want to hear and then forcing those points across seems just plain risky. I mean, maybe try it if you have nothing to lose (i.e. interviewing for a waitlist spot late in the season). Otherwise, you'll risk sounding wierd and/or tripping the interviewer's BS alarm.
Lastly, how many times have you heard the story of the guy or girl who had the perfect interview and still got rejected? I know a couple of people to whom this personally happened. It's not like nailing the interview makes it a sure thing. If the person who interviews you isn't on the ADCOM, there's a good chance it won't even matter that much. If, on the other hand, you come off as psychotic, your whole app could get dumped over one lousy half hour.
If you want your interview to really help you get into medical school, then practice talking about the issues. It'll make your conversation smooth and easy. Or maybe you're just naturally good at these things. That helps too. But don't overswing- you'll strike out or pop up, like all those hitters in that 18 inning game yesterday.
When a major leaguer hits a home run, chances are he'll tell you he was just trying to make contact and hit the ball hard. That's all I try to do.