"Upside down" living is quite common here at the Jersey Shore. So are elevators.. for people.
If it's a spec house, I strongly suggest you go that route vs a dumbwaiter, even if it costs a little more (assuming it can fit in the floor plan). You will limit your field of potential buyers without one. Most fatties, couch potatoes, the elderly or folks with disabilities will not walk upstairs to get to the living floor area, in my opinion.

But, you're the architect. Just know who your buyer is!
Good luck Tom.