This is very well thought-out and I think it would make it a lot easier for people to select (or avoid) material based on the content. The fact that the existing film ratings don't do this for everybody is manifest by the number of websites that exist to tell parents the content of DVDs, videogames etc., so that they can decide whether they want their kids to view/play them.
For "Worksafe", perhaps "Universal" would be a good substitute? In the British Board of Film Classification's system, "Universal" or "U" is the equivalent ofa G-rating in the MPAA system. There also used to be a "Uc" meaning, "Universal and particularly suited to children" which was used for childrens' programmes on video, etc., but you never hear about that now.