In your previous mail you wrote:
It seems to me that Mobile IPv6 could go a long way towards
solving this problem, in conjunction with some sort of automatic
home address assignment capability.
Crucial to effective operation, however, will be the ability to
set up temporary security associations, to avoid unauthorized
redirection of traffic flows to and from the newly assigned
=> this requirement can be a problem for paranoic privacy because
IKE will reveal too many things (the real/care-of address for example).
But if temporary security associations are mandatory, IKE itself is not,
ie. another tool can be used to set up them, for instance AAA (and
its hierarchical service model). In fact, the automatic home address
assignment capability should need something like AAA too...
PS: this kind of services can become very useful in the future here
(to come back to the initial topic :-).