They don’t need this motor, but if it can be scaled down… at over 10kW/kg sustained, one could wish/hope to get 200W at 50g (disclaimer: I have no idea how this scales with size). Combine that with 1kg of a 600Wh/kg battery (https://news.ycombinator.com/item?id=45797452. Again, I have no idea how realistic that is), and you have a bicycle that’s only a little heavier than a non-electric one, but gives you a boost for 3 hours (more if you use it sparingly. If you’re cycling at leisure, 100W already is a lot of power)