Subscribed. I just caught up on the thread and you have some interesting ideas. I personally like the idea of a great handling TDI based model. There is another kit car out there with a small diesel engine.
Kinetic Vehicles
If you haven't followed Jack McCornac's blogs they are on Mother Earth news but their site is hard to navigate.
MAX Update No. 79: Incredibly Good Mileage (127 MPG)