Specifically, I'm trying to use the JobConfigHistory plugin with the Promoted Builds plugin, which saves additional configuration files under jobs/<job_name>/promotions/<promotion_name>/config.xml - though the UI presents the information in these extra config files as if it were just part of the base job configuration.

I'd like to be able to track changes to those files, and it makes sense to me to request a user-configurable include filter to allow general-case handling of non-standard configuration information rather than asking for a one-off fix for a specific plugin.