I'm not sure how the index card system works per se, but I'm guessing that it's similar to the ICal/Kinkless system in that there are lists of Next Actions associated by Contexts. It sounds like you are removing Nicky's NA from one list and putting it on another called, "WF Nicky." If I understand you correctly, your recommendation could potentially neccessitate two Contexts/Agenda's for each person w/whom you commonly have an Agenda. In the above example you'd be maintaining an Agenda called "Nicky" and another called "W4 Nicky."

This seems cumbersome in that Nicky's stuff (assuming there's more than one item on the agendas), lives in multiple places. Ideally, it would be more effiecient to have all NA's regarding Nicky to reside in just one place. Your list of All-Things-Nicky would contain NA's, Someday/Maybe's and W4's. This methodology would be particularly useful if you need to maintain several NA's and W4-NA's across the agenda's of multiple people.

Since your using a paper GTD system you could use a highlighter to flag an item as "W4" and keep it on the original list.