Boy I think I'd look at Doug Jackson's http://www.submarineboat.com
website first for comparisons. He's building a dry ambient where
most of the SportSub's are wet ambient. Doug has a large surface
cockpit/rear deck area which obviously floods when underwater but which
provides a nice seating and cargo area while surfaced.
Doug's design looks different from most any other sub, and different
from Joe's WWII look, but I think it has some great practical ideas and
more similarities to what Joe is describing.