The direct drive approach is an efficiency measure as well.
And the plan is to make the vehicle adaptable. They aren't ruling out AC versions - just working from the assumption that fewer people will shell out for an AC system when they can source suitable DC motors & controllers for much less.
The Miata rear end is a good idea.
My concern about the used components is: you're building a car based on parts that are being recycled as we speak. There are fewer parts available for the car now than when I started typing this reply
