My personal solution is simply put everything online and make it difficult to find what they are looking for. If allowed, charge them for downloading documents. Also slow the movement down by recordings of your favorite telephone contact. "Thank you for the call, you are currently 195th caller in line, wait time is approximately 90 minutes" Then cue the worst music possible.
That's bullshit. Any Govt would weaponise that in a heartbeat to stop bona-fide requests.
A better solution:
First-3rd requests: Copy & send it.
4th request: scan/digitise it, load it onto your publicly accessible web site and post the URL.
All subsequent requests get the URL and - problem solved.