Ability to append to cpanel's default global exim filter using an include file

Exim allows global filtering of messages which takes precedence over account level and user level filtering. Cpanel uses this ability with the file located at /etc/cpanel_exim_system_filter. It is possible now to copy this file and add to it, but when there are cpanel updates it's possible that the original file will be updated while the copy will not. A good solution would be to assign a file to be prepended or appended to /etc/cpanel_exim_system_filter so additional global level filtering can be accomplished without straying from cpanel's defaults.