The problem is that if the department is too small, the curriculum is focused toward the areas of specialization of the few faculty. For many students with a broad set of interests outside CS, this would be fine. However, for a top student like this, I think it would be a mistake and the medium sized research universities would provide the more personalized learning along with sufficient breadth to allow students to get into cutting edge research.
Another one, though not midwest, would be Brandeis. This has a very good CS department with 16 faculty not including lecturers and visiting, is a research university, but has an undergraduate class of roughly 900 per class.
Of course you might put UChicago in the mix too. Their CS department is quite good especially in theory and artificial intelligence. Not an easy admit though.