OK, I've analysed the problem. It comes down to the list of requirements conflicting with each other. These are the conflicts:
Longer range increases weight (battery size), which reduces portability and general handling.
Greater power increases weight (motor and battery size), which reduces portability and general handling.
Larger wheels increase weight due to size of wheels and frame), which reduces portability, etc.
Portability and general handling by a weak person requires light weight (small battery and light frame and wheels)
Foldability increases weight due to extra strength required and additional mechanisms.
Long range requires big wheels since small wheels are inefficient and uncomfortable and big wheels increases weight, reducing portability and handling.
As you can see the main conflict is between the portability/general handling requiring low weight and all the other requirements that push the weight upwards.
If I were given that deign brief, the first thing I'd be looking at is a 201 rmp Q100 motor running at 48v. All the bike components would need to be fairly high spec to reduce weight. After that the main discussion would be about compromising on the range and the importance of foldability.
Other than that, a moped has infinite range, all the power you need and doesn't need to be taken on a bus, car or train, and it would probably be cheaper all round.