I'm not thrilled that the kensei lends itself to be min-maxed for a greatsword. But at the same time, I'm not against having that as an option for people who want to play a more anime style martial arts weapon master. (All we need is to bring back 3E's Monkey Grip feat and the image is complete). But other weapon choices should be encouraged without being sub-par options.
Not doing indepth math checks to see the impacts, but a couple of suggestions:
• Whenever you wield a kensei weapon, you choose whether to use your Martial Arts damage die in place of the weapon’s damage die.
If the weapon does not have the two-handed property, you choose whether to use Dexterity or Strength for the attack and damage rolls of the weapon.
Kensei weapons are considered Monk Weapons with regard to unarmed strike damage and bonus attacks from the Martial Arts class feature.
With that (or something less wordy), the zwei-hander characters are going to have to invest in Str a little more to optimize, which I think is fair. Fighters have to give up a shield to use those types of weapons; Monks may have to sacrifice a little Dex for more damage.
• When you take the Attack action on your turn and hit a target with a kensei weapon, you can use a bonus action to pummel the target, dealing additional bludgeoning damage
equal to your Martial Arts die to that target and to any other target you hit with the weapon as part of the Attack.
Here, I think the pummel damage is still attractive vs Flurry of Blows, even allowing Kensei weapons to be Monk weapons. Especially as it doesn't require Ki to fuel. And the +2 AC can be gained with a more effective unarmed attack.
Jeremy Crawford already clarified on Twitter that pummel damage from a distance is not intended.
Well, that's kinda good news. Means there's still room for the zen archer to get his own subclass.
