I have an imiev and they are lightly-built. I've had a small car with a certain number of batteries which made it thump around if the speed wasn't low or the undulations reasonable. In that car, the battery mass was quite noticeable through the handling with heavy-ish steering and when changing throttle position.
So I wonder what sort of imiev it would be with any significant increase in battery load. Also, if we worry about leaf and mitsubishi outlander battery degradation where the batteries would be fairly consistently made but not tesla-battery controlled, you're going out on a limb intending to go to extreme range with that equipment, let alone have the time for solar recharging, what with cloudy days, low input from panels to many small batteries etc.
Having been through the previous experience, I lost faith in aftermarket-equipment-reliability compared to a 'bought one'. It seems to me that what you want is the promised Tesla 4WD thing which, it is said, will have the battery-bank-gear version for tradespeople.
So, I don't believe you should imagine a high-performance ev for a song (although so many do
.) Songs are light entertainment.
People here love to play with electronics, or they buy brand EV's, drive them and discuss the early-adopter issues that arise. They don't love electronics and drive what they made, unless they live to play with them (outside work hours
Edit: Added )