And yet, even in this position, I think having IPv6 native inside of a production network isn't absolutely necessary (our production env runs in the RFC1918 space too even though v6 would be available at both ends):
Access to the private production network should all happen over an encrypted and authenticated VPN and all access form the production network to the public network (if needed at all) should go through a filtering proxy server.
Which means that the addressing used in your internal network becomes completely irrelevant and can easily be IPv4.
This only becomes an issue once you need more hosts than the /8 offered by the 10/8 RFC1918 network, but the days when you need (and can afford) more than 16.7M nodes on a cloud computing provider are probably still a ways off.
If you want instance level IPv6 in order to access an instance directly or in order to access a resource directly, you're probably doing something wrong.
Then again, as services become v6 only (which will still be a few years off) and you need to access them from your production network, then your frontend proxy will of course need access to the v6 network. At that point, yes, instance level v6 becomes necessary too.