I have to admit that I have trouble following this post, what are you concretely asking?
The solution to avoid stale PRs is to go out and start reviewing and encourage other people to do so. 
If you feel certain labels are missing, open a PR in the ofborg repo when applicable) or write a label bot and showcase it on your nixpkgs fork.
Anyone reading this who is not an active nixpkgs reviewer: please consider reviewing PRs. Your work will be very much appreciated by the community. If you have reviewed a PR, but cannot merge it and it’s stuck, use the PRs already reviewed topic. Also feel free to ping me (@danieldk) in the PR, as long as it is not anything cryptocurrency-related.