So basically: Redomain your utility function by composing it with an adaptor. Where the adaptor is a map from new-ontology -> old-ontology. Construct the adaptor by reverse-engineering your algorithms. Have I got that right?

Edit: No this sucks. Sometimes the old ontology doesn't make sense. I must think more. /Edit

That's a good statement of the problem, but I can see that "reverse engineer your algorithms" is the hard part, and we've just bottled it up as a black box. There's no obvious way to deal with cases that couldn't exist in your old ontology (brain damage can't exist in a simple dualist ontology, for example), or cases where there's a disagreement (teleportation and destructive-scan + print are different when things are ontologically basic, but more advanced physics says they are the same).

Some help may come from the fact that we seem to have some builtin support for ontology-shifting. It does happen successfully, though perhaps not always without loss. On the other hand people with the same ontology don't seem to diverge much by getting their through different update-chains.