Are you not approaching this from the wrong angle?
Why do you need a van/MPV in the first place?
You have mentioned you will not use the rear seats, so I would guess you need to carry something large in the back
in which case it may block you view from the rear windows too.
What are you looking to move what weight and dimensions do you need
Access to the load space etc
If you safety concern is around visibility as someone has already mentioned most recent vans come with mirrors that give a wide view.
Or you could get a white one then no one will expect you to look anyway