https://www.youtube.com/watch?v=ur9F-ygZSDA

Feat: Poisoner Weapon: Blow Gun Feats: Sharpshooter and Poisoner

Custom Lineage or Grung: http://dnd5e.wikidot.com/grung

Fighter Artificer @ 2 (getting the ), Poison Spray for fun... Faerie Fire, Cure Wounds, Guidance Infuse Item @ 3 (Enhanced Defense, Repeating Shot Infusion for Blow Gun) Fighter 2 @ 4... Samurai at 5 Level 9: Fighter 7, Artificer 2 13: Fighter 11, Artificer 2 Level 16: Fighter 14, Artificer 2 (pick your favorite feat, Lucky, Toughness, ASI somewhere) Level 17: Fighter 15 (Rapid Strike from Samurai)

The damage of the weapon does less than getting other features/traits that increase your damage in other ways, so increases in the monk weapon damage shouldn't be a big damage increase (more attacks scales faster than increasing the damage dice size).

Rogue?