Kyujutsu Monk (5e Kensei Monk variant)
by Marc SaindonI'm not really doing a re-write as much as just highlighting sections of the Kensei subclass: while it's the "Katana Monk", the subclass does accomodate a range attack build, so you can specialize in the longbow (see notes about Kyudo) instead of the sword.
Trying to match it with Mystara lore, you might fit the "Archery Kensei" with the Yasuko culture in Davania (Mystara Japan, which I consider to be living in synergy with emigrants from Myoshima, the same Gnolls and Elves cooperate in Graakhalia). While most Yasukan archers will be Fighters, the practice does attract enough devotion as a martial skill that it develops a Monk subculture around it. Strangely, while (in my fanon) Ochalea is phasing out archers in favor of crossbowmen in its army (who can be recruited more quickly), Yasuko doubles down on developing quality over quantity. It also as a strong following among women of the warrior class (onna-musha, see notes) as a means to defend their communities while the samurai men are mobilized on the field. Contrast this with Ochalea, where women have a more limited role in society, especially in regards to warfare and adventuring.
Notes:
Kyūdō
Onna-musha
(Image from: https://www.deviantart.com/bootslover/art/archer-girl-787886295)