My suggestion is to go with a primarily Face build, first and foremost, with Critical Strike (but not Killing Hands, because... well... Pacifist), soft-capped Agility, and 4 in Pistols, and Unarmed Combat. If you want to go the Augmented Adept route, throw in some Muscle Toner, as well as they standard Face-o-matic upgrades.
For his weapon, can't go wrong with a Sakura Fubuki + Smartlink, loaded with Stick'n'Shock. 40 round mag, can fire Narrow Short Bursts with semi-auto recoil. Best option in the game for firing nonlethal ammo at close ranges.
If you weren't doing "Core Only" I'd say take either Speaker's Way or Warrior's Way, depending on if you want to emphasize his current occupation or his past one, and take a Geas for all his powers around only causing harm in self defense or the defense of others, and only if it can't be avoided. Basically, linking his Pacifist to his Adept powers