When listing faculty that I'm interested in, would it be a good idea to list faculty that are in a related department?
I would also agree with sending the email to A. You could also email B to see his view. He may have already worked with MS Stat in the past, for example.

Because the two subjects aren't that too far apart, you may likely also be able to work out something that is tailored specifically to you. I haven't met too many professors who like to shoot everything down, so it never hurts to try.