Is it possible lift:loc is hitting LiftRules.localizeStringToXml instead?
No simpler way to do it comes to mind off the top of my head, though perhaps
you could implement a resource bundle subclass that you then set as the parent
of the application's bundles. I believe missed lookups in the child resource bundles
then delegate to the parent, who could look out for them. This would be more
generic than hooking into Lift functionality to do it. Depends on whether you consider
that a positive or negative, though, and I've never done it before so there could be
caveats I'm not aware of ;)