I didn't know this existed either. I do, however, see a comment by @pharesim which makes me thing the Google Spreadsheet approach may not be the best one:

"voted out another time this log is useless"

Maybe you (or someone else) could go beyond just monitoring the #witness-category and actually reach out to each one individually? It would be a time consuming job requiring a lot of communication with the witnesses, but I do think it would be really valuable to the community. I'd imagine we could create a pool of funds to reward this person beyond just our upvotes on their weekly post.