IPv6 purists think that you can simple have multiple IP addresses on each client, all configured magically, and reconfigured transparently when your ISP changes, with every device somehow knowing via some form of policy deployment (perhaps via dhcpv6) which network to use for a given flow.

That's so much simpler than simple src-natting your clients at the edge of your control and routing your outgoing traffic based on a policy at your natting device /s