BTW, there are some invalid values which have no matching file on OSM Wiki or Wikimedia Commons and never had it - is anyone interested in such list?
I also have list of values where name of file on OSM Wiki changed or files were deleted as unused duplicate of another file. I am slowly fixing such cases but I can give list to someone (I have approximately several thousands of known tagging issues on my list).
I would have the same opinion. If no one has added it so far, a fixme won’t necessarily bring that about either. If someone has a special interest in it, that person will find it even without fixme or t.b.d values.
I don’t think a mere list is very beneficial. If it would trigger an issue at keepright or Osmose, that would make more sense in my humble view.