Hmmm... I'm not heading into I-banking, so I can't speak specifically to your goals. But I am definitely a career switcher. In my case, I was asked repeatedly about why I wanted to switch fields and how I hoped to accomplish this. Specifically, I was asked to describe the process that let me to an MBA, where I saw myself immediately post-MBA, and where I saw myself in the long run. These questions are naturally asked of every applicant, but if you're switching fields, you should be able to do this especially clearly and confidently. I described potential positions in the industry I want to enter, who I had talked to at the lead companies in the industry, and how an MBA would help me get to my ideal position. No one asked me any technical finance or econ questions.
All of that said, consulting to I-banking (and vice versa) is a pretty common MBA move. If you can explain clearly why you want to do this, I can't imagine anyone's going to challenge your financial knowledge. Internship interviews during B-school will probably be another story, though