Okay, you don't want to prosecute everybody in the files because it will collapse the system, so how about a cut-off? Just prosecute the ones who are mentioned above a certain number of times. Like, if your name is mentioned more than a few hundred times, you can get a full-time FBI agent assigned to you.
And if, God forbid, there's somebody in there who is mentioned over a million times, you get a dedicated team of dozens of agents, special prosecutors, and forensic experts who will work non-stop until you're serving a life sentence.
That seems like a reasonable starting point, right? Better than just throwing your hands up in the air and doing nothing.