It's not uncommon. There aren't a ton of lawyers running around b-school campuses, but enough that your application wouldn't raise any strange eyebrows.
I had a lawyer in my section who had studied in the English system. He was a terrific addition to the section and provided insights that no one else in the section could.
I think you'll add a terrific flavor to b-school. One of the keys to your app is explaining why you want the MBA. You just want to make sure that the ad comm don't get the feeling you're applying on a whim. It sounds like you've got that covered.