Personally I will like to echo on:
Social mechanics and I will agree that it would be nice having clearer guidelines on what courtier and artisan characters can actually do.
I would like to see iaijutsu folded into the main combat mechanics.
I wouldn’t mind to see talent trees, like Star Wars, to add more flavor to a pc. Although we never saw a problem trying to differentiate to characters from the same school as we have always played multi clan parties.
Must note that we also never had problems with characters who want other weapons as their main. There were at least 4 schools that used other weapons than a katana as their main: Heichi Bushi, Lion Spearman, Tsuruchi Archer and Yoritomo Bushi, plus others that were associated with different weapons, Daidoji with spears, Hida with Heavy Weapons, Moto with scimitar and Shiba with pole arms.