Wonder if it's possible to have a internal ipv4 local address range that is natted to ipv6 public address on your router...
This is the opposite of what OP is asking. He's wanting internal IPv4 with external IPv6, NAT64 provides the opposite.
IPv6 Discussions
This is the opposite of what OP is asking. He's wanting internal IPv4 with external IPv6, NAT64 provides the opposite.