Is there no way to just have a script add a comment on every new PR saying "Due to insufficient staff, your PR may not be reviewed for a considerable amount of time."?
Your code is important to us. Please stay on the line, and the next available reviewer will answer your code. Due to unusually high code volumes, this response may take longer than usual.
I think the issue is about letting people know that PRs won't be reviewed/merged before they bother putting a lot of effort into them (both the commit itself and setting up/documenting the PR).