As someone who once in the past had to handle (an ungodly amount of) FOIA requests, should there be a list? I don't know, primarily because I don't know what the utility is. That said, some opinions derived from experiences:
1) Some people are serial filers. They haven't bothered to do the research up front to ask relevant questions and after a bit when you see their names you know that when you read the next paragraph it's going to be asking about a) things you know you cannot disclose (not for some BS reason but because of things that actually should remain secret), b) aliens (no we don't have them), c) blatant evidence of government conspiracy, generally of the NWO sort (duh and or hello? Project BlueBeam doesn't keep paper records!).
2) There were also frequent filers where the requestor isn't a crackpot, a FOIA spammer, or asking for something they know in advance could not be provided. These were generally authors. We always got these people what we could and even though my shop didn't keep a list me and the other poor souls stuck on FOIA duty knew them by name. This meant that we basically knew what they wanted when they filed which helped us get them their stuff faster with less overhead. (N.B. this did not stop us from cursing them for their curiosity and the resultant carpal tunnel).