The means to create/purchase "badges" or some other sort of trinket to identify custom PC faction members would be really cool, not unlike the ones for current factions/associations such as the Stonebuilders, veteran badges for Peers, or others like this that have been available in the past.
Making this "badge" customizable in not only name/description - but form, look, and "flash" message would be a HUGE plus and make it so that each can be somewhat unique. As well, maybe a way to ensure they can't be copied by the uninitiated, but require a true forger or equivalent to do so.
In the case of PC factions that are open and public, this could help promote the face of these factions in addition to, or conversely given the lack of, custom uniforms or colors. In the case of the secretive, it could allow hidden members to identify themselves to one another without saying a word - and also for those who hunt them/look to distinguish them to get a clue, whether by seeing the flash of the badge or finding it when searching them, etc. Could be fun!
As much as badges are cool, it isn't something that's impossible to RP.
Just set up a little macro like the other ones on like cntrl F12 haha, and RP having badges.
X (Player named) flashes their Y (pc faction) badge.