"incidentally, all IPv4 address can be directly mapped into a subset of the IPv6 address range"
Not so easily. From a pure mathematical point of view, sure. From a network one, it's far more difficult.
How do you map the network part and the host part of any IPv4 address into a IPv6 address - and still being able to route it properly to destination? One of the design goals of IPv6 was to improve routing and its performance.
Biting the hand that feeds IT
