It sounds cool, but I'm pondering on whether it is implementable, due to the way the system works.
But seeing how the match system works, I doubt there is any need for it anyway, since in APB plotting things is not illegal, so you can stand outside a bank with a bunch of criminals for hours and not get arrested. As soon as you commit the crime (and I am not sure how it works with if it gets noticed or just right away) the system will match up some enforcers in the area to go check it out, and when trouble starts send out an APB to non-busy enforcers in the area, or non-busy criminals in the area to help out the crime.
So essentially undercover sounds cool, but I doubt it can work in APB, because the goal of an undercover agent is to prevent a crime before it happens by leaking information, and in APB that seems like a rather impossible thing.
Though who knows what kind of crazily cool things Realtimeworlds might add in the future