I think that this was the purpose of the keyword nodelet (see New Keyword Functionality and Re: Re: topic-linking for nodes). The node author and the janitors can change the keywords, and everybody can suggest them. Now we just have to get the search and Super Search to search on keywords. (I take it that this is already on Our Fearless Leader's long TODO list...)

In the long run, I think this is a much better solution than lots of metanodes with no actual content other than links.