The hard part is coming up with a way to do the host/location mapping in a way that is simple, fast, cheap, secure, flexible and reliable.
Wouldn't we all start deploying, e.g., HIP tomorrow if we had a solution for this?
I'm not exactly current on what's happening with HIP but aren't there supposed to be working implementations today?
And, how might that solution be any different than MIP HoA/CoA binding management?
One of the main mechanisms we're considering in the multi6 design team (or multi6 DT #1 I should say) is a distributed database that holds the mapping from identifier to a set of locators. For multihoming this makes a lot of sense as you know all your possible addresses in advance. With MIP this is different, but there you have the advantage that the home agent is (presumably) always available, while the point of multihoming is to survive failures.