Forget IPv6 NAT; use LISP instead

Well, it's much easier just to register in ARIN/RIPE and get PI assignment. It'll cost about $3000, which is far cheaper than two colocated servers/routers with BGP and LISP support. And I'll get all those benefits and without need to setup LISP.

We've actually considered a similar variant (colocate a server and use it to terminate GRE tunnels).

So while there may be other ways (I'll concede that multiple IPv6 addresses might work for somebody), your choice is still is very much between spending $$$$ and having in many ways inferior solution.

As for LISP, it merits its own article on LWN. And right now it's FAR from being really complete (which is OK, people are still working on it).