The Wankel was low on efficiency but that may not be a problem with limited use as you suggest. I always liked the Wankel.
> The Wankel was low on efficiency
Yes, early Wankel’s got poor gas mileage. However, it did improve over time. The idea here would be to allow the car to be used even in areas where there are no ‘zinc fill-up’ stations without the risk of getting stranded. A gasoline-powered range of about 100 miles lets you cross just about anywhere.
Wankel engines have the highest power/weight ratio of standard internal combustion engines, and I think I read that they could be built with internal magnets and coils to function as an integrated motor/generator.