What I'd like is a system to let me browse, create and organize my "notes," to use the Anki term of art, in a literate, flexible way. You could probably build it on top of Anki using tags and/or data hidden in HTML, but I think it would provide enough added value to justify paying for it.
Basically, I want WorkFlowy for Anki notes. I should be able to organize my notes into hiearchical categories and browse them easily. Currently, it's difficult to find the gaps in your Anki deck on a given topic unless you're very careful and thorough with your tagging. And even then, only being able to view one card at a time makes it hard to quickly scan through the cards under a given tag.