Will discuss, but the problem with this is that then people would want referendums on a lot of different levels (guild, message group, etc) which may or may not be practical.
Apart from message groups i don't see why guilds/religions too can't have referendums.
Ducal referendums are most potential thou, it makes allot of ducal identification amongst knights if they feel they have something to say or directly influence it's politics.
I've been trying to achieve it since Madina was founded but it is very hard without referendums or other ways in which knights can influence or benefit the duchy directly.