Zoltan,
I just stumbled across your thread.
Kudos to you on a beautiful design!
I think you have a great starting place.
I like the idea of the two people in front with two smaller folks in back. With my wife going to have a baby soon, we need at least a car that can handle two people plus a car seat.
As efficient as tandem seating can be, it is not "mainstream". People think it's weird. I think folks like the shape, but if there was something about the doors or seating that was really unusual, it would be a turn-off. That's one thing I found out about the Tesla when I got to sit in it. It's really hard to get in and out of! A friend of mine test-drove a Volt and said that wasn't real easy entry/exit either.
For the final drive system, I would encourage a gasoline/plug-in electric as a minimum. I am a fan of battery-electric vehicles, but for good range, they tend to get expensive or heavy real fast. I think that PHEVs may be the best of both worlds. (I am secretly considering converting the Electro-Metro into a PHEV with a propane generator.)
As to the theoretical Grandma's house 35 miles away, a Chevy Volt could get there without a drop of gas, a Nissan Leaf could do it with one battery tied behind it's back, and even a 35-year-old Citicar could get there.
That said, our culture does have certain expectations of cars, including that they be able to go rather far on a single trip.
I am always amazed at the response on the masses on the internet. Many of my web videos are met with replies of the ignorant, who are convinced of their own perpetual motion machines, or the critics, who would rather destroy some other's work, rather than to attempt any of their own. (Don't let the Muggles get you down!)
It's great when you find positive folks who help support creativity and collaboration. The Open Source EV Controller on this forum is a GREAT example of this.
One thing I will say about designing the body before the drivetrain is this: drivetrain effects body design. For an EV, you may want to put all that ballast to use nice and low, like built into the floor. For an internal combustion engine, room is needed for radiator, exhaust, etc. (I LOVE the grill though!) I have no idea what would be needed for the steam engine, but I can only imagine that it has it's own unique space and shape requirements.
I'm sure you already know of it, but this project reminds me just a bit of the
RQRiley XR3 which is sold as just a set of plans right now. That is designed as a two-seater diesel/electric hybrid. A friend of mine has the plans and wants to build his as pure batt-electric.
Your story also reminds me a little bit of Bob Beaumont and the Citicar. He asked Club Car to build him a custom electric golf cart with a windshield and headlights. Once it was built, he literally drove it to Wall-Street to attract investors. In the end, he built well over two-thousand cars. Later, he designed the Tropica - an all-electric roadster decades before the Tesla. Only twenty-some of those cars were built, but they still have plenty of fans.
Bob's story is recorded in the book, THE LOST CORD, by Barbara Taylor. Parts of the story are sad, but overall, I found it amazingly inspirational at one man with a vision could do. Last spring, I met Bob Beaumont, Barbara Taylor, Bob Stone, and some of the others involved in the production of those vehicles.
I also agree with some of the comments made earlier about the Aptera trying too hard. There doesn't have to be any one single vehicle which is all things to all people. I just wish that there were some vehicles that tried a little harder at being better. Unfortunately, our commercial/capitalist/consumer culture makes that a bit difficult.
For now, I'll stick to my Electro-Metro, but if I could purchase a Zoleco off a used car lot, I sure would.