RVtrader.coma and PPLmotorhomes.com are good websites to research the Class B market. IMHO you are better off buying a proven model that has been built for at least a few years so they have gotten the bugs out of it, instead of trying to customize something. RV shows can be a disappointment. At this year's show in Houston, there was not much to see in the way of Class B's. Quality of construction and driveability are more important than little wrinkles with the floor plan, etc. Go for simplicity, you may not need a generator or want a macerator for pumping out waste water, gravity is 100% reliable. Good luck with your search.
Jim