There are cases where libraries use custom/local class numbers. We should make this a pluggable option so custom routines can be filled by local plugins.
+1
It is a little bit pluggable, but very old-style and pre-plugins and hooks. If you put a .pm in the right spot with your class splitting rules, the GUI will show it in the pull down for selection and you can configure it. It works similar to the value builders.
Just in case a workaround is needed and to keep the use case in mind for people who might need/want to transition.