Ok.. So I came up with this idea...
At the moment, you can either have lots of different windows, or one window with tabs. Well I was thinking, why not two.. or three.. windows with tabs? Then you could separate your friends from your family, for example:
I think it will help users organise their contacts so they can customise it to their liking.
Not the best time to submit an idea, as I know Patchou is busy and won't be adding anything new any time soon, but maybe for the future?