https://www.amazon.com/Xiaomi-Electr...gateway&sr=8-2
One of these would be the best bet. I noticed on an engineering document a while ago it said they were only using 1900 mAh 18650 cells for their battery pack. If you swapped to 3500 mAh cells you could really increase the range and speed on one of these with a new motor controller and a temp sensor. It would be a cool project to work on, but my city isn't urban enough for something like this. They aren't super light weight either. Maybe with the more energy dense batteries in series and parallel you could shrink the pack size and swiss cheese the frame a little lol.
I've had one up to 20 mph here down hill (bird scooter), but the electric scooter law is 28 mph and below. Would be a wild ride at 28 lol.