While I absolutely think that there should be a mechanism for an ontology to update imported terms, I think this suggest something even more important - the import system itself is still broken. We are making large strides on a new solution which we case the "base approach" which will lead to a much more clean dependency management. It avoids pulling in terms from ontologies that do not belong there. However, the issue with using obsolete classes in axioms wont be solved by this. So, if you import, say APOLLO_SV:1 and APOLLO_SV:1 has an axiom, APOLLO_SV:1 part of OMRSE:1, and OMRSE:1 has been obsoleted, these is a tricky issue to solve automatically. One brutal solution would be to not ever import axioms that reference obsolete terms. Another one, more gentle, would replace obsolete terms with their replacements, if any, and delete the ones that do not have a replacement. Interesting problem!