1 How about using tags/links to associate attributes with requirements?
2 This could be as simple as adding a link, fo e.g. :
4 * If it is traceable or not
5 + \[[attributes/traceable]]
6 + \[[attributes/untraceable]]
7 * Its criticality level
8 + \[[attributes/level/critical]]
9 + \[[attributes/level/important]]
12 + \[[attributes/priority/low]]
13 + \[[attributes/priority/high]]
14 * If it is functional or not
15 + \[[attributes/functional]]
16 + \[[attributes/non-functional]]
18 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.).