An e-bike without electrical assistance is heavy and sluggish, much more than a normal bike. I don't think anyone by them for the aspect of becoming a normal bike when out of power, they buy them because of the assistance.
Are you talking about those with brushless motors? The other kind, geared motors, should not impede anything when offline if I understand correctly. Then you just have a heavy bike, which is a problem in a hilly city but not so much in a flat city.
In particular, heavier by at most 2 kg. If it's a hub motor, all it needs is new spokes and hub. If it's a mid drive, you might have to experiment a bit.
My experience is many e-bike owners run around with almost deflated tires, worn out chain, rubbing brakes etc., since they themselves don't feel the added resistance, hehe.
