I've done some thinking now!
To make the cultist circle work in Zone Idle, it could build off the confirmed Existance of the Canon STALKER factions.
Lore:
Mechanic could offer a quest. Something like "Coming in Contact," where the mechanic asks for a bunch of parts (e.g. PC fans, wires, ect). This unlocks "The Drone" in the hideout. Lore-wise, the drone is ran by Ecologists, who are running a program where PMCs in the zone can turn in artifacts in return for rewards.
Gameplay wise:
Find and turn in artifacts for rewards. Uncommon tier artifacts give an hour long time and so on (whats better for an Idle game then waiting?). Higher tier artifacts return better tier items. How this would work I have no clue, but Idling is best when you're wondering what you're gonna find.
(Sorry for the total Yap Fest!)