Something similar to the tango in shape (passengers front to back, so its thin enough to park like a motorcycle
Commuter Cars - The TANGO, ultra-narrow electric car for commuting; 0-60 in 4 seconds) but with a 250-500cc (bio)diesel engine and 6 spd manual transmission.
Might have to be slightly wider than the tango because it wouldn't have the heavy battery pack to give it stability.
I'd keep both electronics and amenities to a minimum both to save cost and fuel demands (no power anything). On something so small and light, power assist steering and brakes would be unnecessary anyway. Also, that way it would be cheaper/easier to maintain (and mod
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Essentially a fully enclosed 4 wheel motorcycle with a diesel engine.
Because the 70mpg I get on my ninja doesn't seem worth it during the winter rains.