Yeah but there are millions of people with the right assist system that could use a bike for transportation with an assist, that without it the method would be totally impractical. It isn't even so much of a sweat issue ( though their co workers would disagree) but a practical one. Trouble is cost of an assisted bike vs cost of a scooter is a big deal. A brand new scooter that would probably be faster and more practical isn't but about $1500 or less the last time I checked. Yes you need a license and insurance, but if you are going to tap the transportation market thats your competition. Unless you don't have a drivers license for some reason like a DUI, that shouldn't be a barrier. The insurance for those little things are not too bad either.
Since even a mid range bike can cost that much before you start adding assist, either the bike has to suffer or you have to be able to build the assist dirt cheap. IF you are looking at this as an engineering exercise, then design away. You just might find a way that can do a great job, be tough as nails, be totally reliable and be dirt cheap. Never know what you are going to learn when you experiment. IF you are looking to market this for money, I honestly do not see the market with current technology.