Can you really assign the weight of the driver fully to the rear axle? It's not in a terrible location, but it's generally closer to the front than the rear. Also, not too many people are going to be driving a GTI with spirit when loaded with passengers and/or 200lbs of stuff in the trunk.
FWD cars with forward weight bias can be made to handle fine - but there is a reason there are so many RWD 'balanced' converts. You're not likely to get the feeling of a pendulum with the pivot point at your hips that a truly balanced car gives you. And with RWD, you effectively have a second steering device in the gas pedal.
Also, you're ignoring the fact that as soon as the car is in motion, the balance point changes. As soon as your brake for a corner, the weight shifts forward, making a front heavy car severely under-steer, and even a 50/50 car under-steer on corner entry. This is why many race cars have a rear-ward bias.