I like the idea of devotion, and I like the idea of uniform decks. What I think would be cool is creating a neutral equivalent (call it Soldier of fortune, or mercenaries,) which only triggers with no faction cards. You could even take it one step further and attach it to Bandit, Witcher, and Dragon archetypes which would all get a few new cards. Best part is that this archetype works with any leader ability in the game.