Your ability to implement this as a network operator is also constrained by what your network devices and client devices support. Since there exist devices that don't support DHCPv6 and only support SLAAC, /64s turn from a best practice to a requirement. Since everyone made fun of NAT, NAT66 implementations did not exist until very recently and they're still uncommon, even though it's been technically obvious what to do since day one.

You can implement IPv6 by ditching all your network hardware, installing commodity Linux boxes, writing some patches to iptables, and insisting that nobody bring Android devices onto your network unless they run your in-house fork of AOSP. I just think most people would not consider that an option in scope.