Hmm, I've been influenced by my environment.
My environment is a Ethernet / DSL environment. I've been imagining
deploying IPv6 in the N:1 model that's been mentioned earlier, so all
CPE WAN interfaces within e.g. an exchange, are all sitting as nodes on
the same /64. The N:1 model is attractive of course because at a
minimum it avoids all the (pseudo in the case of ethernet) point to
point "WAN" links, and the question of whether to assign global /64s to
the them or not .. the question that's being asked :-)