Some other thoughts...you can buy a car, and run it thousands and thousands of miles without doing anything but putting gas in it. That's the kind of reliability you need on your velomobile- otherwise, half your potential market won't buy it. That means some sort of flat-proof or very nearly flat-proof tire. That means tires you don't have to air up everyday. (That also means inventing something new, because the airless tires currently out there tend to be lacking.)

For similar reasoning, you need an automatic transmission. People that use multi-geared bikes all the time think it's the easiest thing in the world to deal with, just like people that drive standard transmissions in cars think that's pretty simple. But there again, half your potential buyers are going to reject anything that requires shifting two different sets of gears, no matter how utterly simple it is.

I have mixed feelings on the electric assist. I think the theory is that Mr. Ace Cyclist rides it, pumps in his 200 watts, the electric assist throws in another 100 or 200, and you have some good performance. The problem is that there are two different theories to riding a bike. Theory #1, it's an exercise endeavor, you throw some muscle into it, breathe hard, get sweaty and tired, but go fast. That's a lot of the people on BikeForums. Theory #2, you ride a bike because you're too lazy to walk, so you ride it by putting out the least little amount of energy, which means riding at 6-8 mph on the sidewalk. The problem I see is that you want Group #1 to use electric assist, only they don't need it or want it. So Group #2 is who's going to use it, and they're going to throw in their 25 watts and depend on the electric to do the rest. So you might as well just go ahead and design a non-electric version and a non-pedal version (IE, electric motorcycle).

Lessee...what else? Full coverings for weather that are completely removable when it's nice, and quickly removeable and easily replaceable. Either that or an AC system, which seems unlikely. Windshield wipers or some way of seeing when it's raining. Lights on front, on back, on the sides. It should be up high, not like you're laying on the ground. If if has cargo room, you need to be able to load that cargo room without it falling over.