+ \[[attributes/non-functional]]
You just have to create pages for each attribute you want and then pagespec could be used to filter requirements by attributes. I think something similar is used to trac bug with ikiwiki (linking to a \[[done]] page, etc.).
+
+---
+Generally speaking, I think it's always a good idea to get back to the "basics" for something, that huge and expensive tools were made for. But I'm doubtful if such a text oriented tool would really fit all needs of a requirements engineering tool... so what is your real world experience with your requirements engineering tool as described?