First answer: allow users to choose scalable or not. 😉
In my opinion, visually indicating importance that is not important. Other opinions may vary, though.
Applying importance to cetain tabbles sure smells like tagging a tag, which is why you got rid of categories. I believe users can create tabbles to indicate importance… imagine a "hot" tabble, or a "draft", "current". "expired" set of tabbles. We can use your tool to convey importance in ways that makes sense for each of us!
(Just let us drag tabbles to tabbles! 😎 )