This idea crossed my mind as I was searching the section for materials I could find useful. Basically, the topic name gives it away: I propose to assign one or several levels (e.g. **; ***) to each of the items, except, maybe, published research works having to do with linguistics in general or vocabularies.
I think the point is clear, just as an example, I'm trying to improve my both English and Spanish by reading stories and books. On the other hand, when the level is not specified, I spend more time trying to find what I need: while I read simple stories for beginners in English not slower than a native, I'd benefit from reading the same thing in Spanish, although more advanced reading somethimes baffles me.
If someone more familiar with the site structure proposes some alternative or points me to it, I'll be glad to learn more.