If I'm getting this right I don't think NIPs would be useful. I've actually always thought we could just use manually specified URL paths for this kind of arbitrary filtering. But there was also a proposal for algorithms in REQ filters which might be a good idea to revisit at some point. On the other hand many people who are interested in this kind of stuff have migrated to using DVMs instead of relay-based commands. I don't know anything, I would have to get a more concrete picture of how this works in the UI to have a better opinion.