I think with much larger address space and the availability of /56 or larger spaces for many connections means many of us already have excess, the second approach is worth investigating. Come up with DNS management and a system for automatically configuring AMPRNET6 routers to share trust information to tie the network together securely. As I said before, I could easily allocate part of my /56 to this project. I'm using less than 1% of my address range (1/256th to be exact :) ).
Address space is not an issue with IPv6. Everyone here gets a /48 with their home internet connection. I use only 3/65536 of mine :-)
For a "global IPv6 space for amprnet" we would get a /32 and map it 1:1 with the existing net-44 addresses. That will give every net-44 IP user a /56 network on IPv6.
However, I too don't think is the way to go. Just use the space you get on your own internet connection for your own purposes on AMPRnet (and nag the ISP when they don't provide IPv6, give you only a /128 or /64, or assign dynamic prefixes - bad concepts in IPv6 rollout!).
Extend the current DNS server and robot with AAAA records, and find or design some method of sharing the prefix list. Could be done using a BGP server. (not the internet BGP but a server on AMPRnet that distributes prefixes)
Then we can interconnect on internet without the hassle we have now, and still are able to route the same addresses over wireless networks.
Rob