Not sure where the OP is getting ipv6 from, but DS-lite is not actually common, because most ISPs are still providing ipv6 as an extra not exclusive, or people are using tunnel brokers. So most do not provide ipv6 only. However if you have a lot of ipv6 machines behind one ip provided and you want to know what to do the OP's question is sensible. The answer alas seems to be to just run your own NAT alongside ipv6. DS-lite is just getting someone else to do your NAT.