I saw one other playable Cultist mod, but it was a little rough around the edges so I decided to make my own.
I had to give the Cultist something, so I gave him Junkan, as in my head, Cultist would be too afraid to enter the Gungeon alone.

Loadout:
-Dart Gun, infinite ammo
-Junkan

-Minor increase in movement speed (Kids are nimble, man)
-Minor decrease in reload speed (Kids have bad motor skills, man)

Requires Kyle's Custom Characters Mod (https://modworkshop.net/mod/24802), big thanks to Kyle everyone.
Uses the Convict as a base, for anyone who cares.
Only missing punch out sprites, I'll get to them sometime maybe.