This is an old post about ipv6, but it inspired me to go looking, and I wanted to share my findings.

1. for globally routeable IPv6 addresses, probably do let it happen automatically, either direct from the ISP, through the router by prefix delegation, or your own implementation of prefix delegation.

2. for devices you want to access, internally, create a ULA within the fd00::/8 space, and assign numbers (and names) however you like. Translate all your 192.168.x.y IPv4 addresses to fd00::x:y and go. Only limitation is you won't be able to access those devices, using the ULA, from outside your network.

3. you can do both of these on the same subnet, and devices pick up both addresses then use the global address for internet and the ULA for intranet.

That means you can do dhcp, dynamic DNS, private domains, and all the stuff you know about IPv4 for IPv6, and still do all the stateless autoconfig that "they" want. Some devices, like my android phone, never played well with dhcpd6, but immediately preferred IPv6 as soon as I let them SLAAC.

If the prefix assigned by the ISP doesn't change, then device SLAAC address shouldn't change, either, because they're calculated from MAC, so if you need to access some internal devices from the internet, you have to mark that address, but (IMO) marking the full address is not that much worse than marking the prefix and remembering the device number.