I believe that this has been discussed in small ways before, but never made into an official suggestion. We already know that interests are meant to be 'action' items, which can be given and taken. However, there are many concepts which we have, and would like to have, in a searchable function which are not truly 'interests'. Those we have so far include, but are not limited to: adventure, warfare, sizeplay, drama,, domesticity, friendship, etc. There is also the potential for further suggestions like exercise, small dom/big sub, and a plethora of other items that would be useful to search, but are not interests.
I propose another section be added to the profiles, outside traits and interests, that be called themes. These would not need have the give/take, thus eliminating the sometimes awkward decision, and would be meant to set the desired themes. I, personally, imagine that they would be divided something like interests (with themes core to a character, okay to play, possible to play, and never to be played.)