Hmm, the Kensai is cool in that I see what they're going for, but it badly needs another pass- from what i can tell the purpose is that as a Kensai, you give up your normal bonus action shenanigans for an aoe feature that's a little lackluster.
I love the direction of being able to use all kinds of martial weapons and stuff though.
As far as I can tell, the intent is to make great weapon wielding monks.
The Pummel is not an AOE, it hits at best 2 targets (barring Multiclassing into Fighter and using Action Surge).
What bothers me about it is you have two sets of abilities, you have wielding the big weapon, and you have accuracy buffs.
Let's say the 3rd level stuff gets fixed, what are we left with? Weapon is magic, increase accuracy for 1 attack once per rest, make your weapon super magical (for accuracy and damage) and re-roll a missed attack.
You want to play a super-amazing Heavy Weapon Character: Do you choose Fighter, Barbarian, Paladin or Kensei? All the other classes support big melee weapons better than the Kensei does, so really for most of the game (until level 11) you are a middling weapon wielder with monk abilities.
If the concept is being a great weapon wielder.... play something else would be my first recommendation, because nothing in the Kensei is worth trading the abilities of the other classes for if your goal is to be a big weapon wielding monster.
On the Tranquility monk, it is important to note that the monk has no penalties for getting in combat, other than losing Sanctuary once he actually starts fighting...
*Re-reads sanctuary*
ROFLOL
You can totally play a Jackie Chan character, who runs into a large group of enemies, and keeps asking to not fight, while the enemy keeps getting their blows redirected into each other, showing that violence hurts you more than the person you aimed it at.
That is almost too perfect, crank wisdom for that save DC and allow the orc horde to tear itself apart while trying to kill the guy in the middle.
Then, you can still break sanctuary and be a normal monk, taking down enemies who refuse to listen to reason to protect the innocent. The flavor isn't pure pacifist, but "violence is my last resort" type of character.