I've actually been half kicking around a feature request on this idea...allowing a knight to join an army, and having armies align to a particular "banner", then having war diplomacy built around "banners" rather than the diplomacy chart.
and yes, I know how much work that would be
but think of how many options people have asked for - and some are even seriously being considered, such as Duchy Armies and Duchy warfare - if this type of coding were put into place. think it is worth discussing a little more
