Aren't we missing the point here somewhere?
The Zed is a GT car hence thearge fuel tank. It's filled with all your creature comforts, and that signifies it's purpose was not to be super quick off the mark, and handle like an Elise in the corners.
As others have said, had the weight issues been taken care of, it wouldn't have the luxuries or huge fuel tank.
We are discussing a car that was made as a GT and turning into a slim tuned track car. Personally I chose the Zed for it's ability to serve a number of purposes, looks, power, price and luxuries. It's served it's purpose very well. It's not too difficult to reduce the weight of the car but it depends on what type of car you end up with. I've reduced the weight by 66kg and haven't compromised the comfort of the car. If you want to lose 200kg from the car it's not that difficult to work out how to lose that weight. Same applies for adding power, not difficult to understand how to add this.
I don't think we should ask why Nissan made the car, or how it should have been better. I bet you could name a large number of cars and how to make them better. Although if that be the case the choice of cars out there dictates you've bought the wrong car. I have changed the cosmetics and tweaked performance and handling. If I wanted a super light super agile car I would have thrown in another 40k and bought a Porsche.