In regards to Iajutsu and Kenjutsu couldn't we make both usable in the same situations but in different ways?
Iajutsu is the art of the draw after all, so in a skirmish it would focus on taking out a single foe in one slice, but with the risk of lower defenses thanks to having the blade sheathed.
Kenjutsu would be more balanced for skirmishes, and reactionary in a duel, again focusing on defense whereas Iajutsu is focusing on the strike.