Thanks for asking. Yes it seems ok. I never thought of doing it that way. It sounds like something comprehensive that is sure to cover the needs of all.
(I got log parsing running on my Jenkins slaves this afternoon. Almost all the rules are set up. After some 6-hour jobs run, I'll see if any more messages need to be suppressed. The web page for viewing the console log is impressive. Easy to use and intuitive.)
I'm using a lot of svn:include properties, so handling data shared by several jobs is usually accomplished with an svn:include. If I could specify a workspace file for parsing rules, then I would use Ant concat to put together the rule file contents.
I like how some of the other configuration sections report with a red message when Jenkins doesn't see the file at the workspace path the user specified. Is this hard to implement?