Hmm.... I don't have many thoughts on Tranquility -- I've played pacifists, had pacifists played in my games, and seen another half-dozen ways of doing them. My experience is that it depends more on the player's style than the mechanics as to whether the character feels like a pacifist and that any build intended to be a pacifist, even pacifist-lite, is going to be role-play balanced and open to abuse if that's not enforced/considered. This build looks acceptable, overall, but it doesn't excite me. (I.e. if other folks like it, I have no objections.)
My first read-through of the Kensai, on the other hand, made me want to play one. That d4 pummel is wonky and kinda WTF. I also didn't catch that a "Kensai weapon" only damages as a Monk weapon, but isn't actually a Monk weapon. I don't think I actually like the differentiation. It just feels wrong. Without the flurry of blows, it just seems tacked onto Monk instead of being integral.
As far using the Monk chassis vs, say, Fighter, it's mostly flavor and about the mythology around the character. The Fighter makes a good base for any archetype that might be considered a soldier, knight, or other "standard" warrior who wouldn't be completely out of place in the military -- even if just being press-ganged. On the other hand, the Monk is more of an aesthetic; they fold some form of contemplative focus into their art. A Kensai may be equal to a Samurai in skill with a blade. Both may say the blade becomes an extension of themselves. The Fighter is all about what the technique does to the other guy. The Monk is about what the technique does to/through themselves. At the end of the day, the bad guy is equally dead. It's the road that's different. Hopefully, the choice of which class facilitates the flavor the player is looking for.
There's a balance. Towards one end of the spectrum you have the trio of combat guy/skill monkey/spell caster. Towards the other end, you have new classes for swashbuckler, assassin, man-at-arms, and chevalier as well as each wizard school, etc. I think the 12-16 range is ideal, with some mild Venn diagram overlapping being permissible.