So what do we actively suggest? Just to reitterate, I want to support IPv6 
  autoconfig on a multi-interface host that does not forward packets.

It appears that NetBSD 2.0 supports this ok.  On a machine with two
interfaces, I set

net.inet6.ip6.accept_rtadv=1

and ran 'rtsol fxp0'.  I got a prefix, and a default router (there is
v6 service on that link).  I started up rtadvd on another machine, and
then ran 'rtsol ath0'.  I got a second prefix.  There were two entries
in the default router list, and one of them was chosen -- the fxp0
one, that I had gotten first.  I was able to ping both addresses on
the fxp0 link, the machine running rtadvd over ath0, and a machine in
another AS.

The only issue I can see is that the choice of router is pretty
random, but if you're a host and it delivers packets, that's arguably
good enough unless you want to participate in a routing protocol.

Have you tried this?  Did it work?

-- 
        Greg Troxel <gdt@ir.bbn.com>