I'm not sure if this will work as a change to the styles-file requires a complete re-import (it doesn't work with the diffs), but as I read even tiles.openstreetmap.org does a complete re-import once a week to fix complications with the diff-import, so there might be a chance..
Peter
Thanks very much. Maybe at one point we should have a script that combines the original OSM file and additions from individual map developers into a single file so that updates are easier, but maybe it just works fine even without something like that.