I would change
- Motor top speed to equal cruising speed for good acceleration and hill handling (you can switch field weakening on to go a bit over)
- Don't size your single speed vehicle for a party trick or bragging right number which will make every other metric such as acceleration, hill handling worse
- Full suspension frame is a must have unless you want a crash on the first pothole you hit or first time you get ran off the road, also having a bike you can take for a spin off road without rattling you or itself apart doubles it's value
- If you aren't planning predominantly offroad, mid drive is pointless, adds weight, cost and a lot of stuff to break (have a cyc)
- Fat tires try to keep light by sacrificing wall trickness, making a blowout more likely. No bike tire is rated above 30mph especially not fat bikes which use tubes which add friction and heating, use regular heavy duty touring tire for 40mph top speed or moto tire if you are adamant on 60mph (which will drain your batter in 10 mins)
Result will be lighter, safer, cheaper more comfortable, better on dirt roads. Far superior all round.