You shouldn't have any blind spots for lane changing when you're using just the side mirrors. It may take adjustment, practice using them, or even adding more/better wide-angle mirrors, but they should give you a good awareness of what's happening around your van. Look at tractor trailers; no rear-view cam, good mirrors, no problem changing lanes.
I've installed backup cams on my previous non-Sprinter B and my current small C. They're aimed down, to pick up the area right at & behind the rear bumper, used when backing.
Jim, "Never trust an atom. They make up everything."