I've been thinking a lot about the rules of the game. What I like and what I don't. I have to say that I think the Skill/Knack system is a little clunky. It might work better if they hadn't introduced so many new skills and knacks throughout the various splats. Also, I wish combat were more streamlined. My biggest beef with combat is that there's too many defense knacks. Maybe a system where you get one defense knack and can use different advantages for bonuses in specific situations?
Maybe combine skills/knacks into a "career and hobby" system, where you just pick your character's base career(s) and their areas of study and get to use those careers as catch-all knacks for whatever a career hobby could cover. So you get to roll Sailor for most things at sea with an even bonus (you're equally good at climbing up to the crow's nest and balancing yourself once you're in it). I think that maybe the swordsman knacks could get revamped, too. So many of them had more detailed abilities than the mastery level abilities. Maybe instead make schools have 5 ranks (like in L5R), with knacks adding new special abilities.
Anything else you can think of?