How to add new job types

I've recently posted several times to the OEM Extensibility forum (http://forums.oracle.com/forums/forum.jspa?forumID=219) but it doesn't seem to get much "traffic".  I've been struggling with creating a plugin and have slogged through getting it imported, deployed, and some simple metrics running.  Since "jobs" don't easily take parameters I'm attempting to add new job types to get several tasks done ... another option might be to add some more specific OS_Command job derivatives to the job library if that's even possible.  I need to do as much as possbile from the command line since we will ultimately be updating many "sites".