I don't want to use the foreign-chars-option to keep the category-names within the URL. Is it possible to change the following chars automatically while building the individual directories but not to a simple "_"?

ä -> ae

Ä -> Ae

ö -> oe

Ö -> Oe

ü -> ue

Ü -> Ue and finally

ß -> ss

Everything else (special characters etc.) should still change to "_".