I’ve recently played an interesting mod for a survival game that implemented raidable bases owned by NPCs on PvE servers. These bases would spawn in a fixed numer all over the map, at random locations, and you can raid them for materials and other stuf. The bases have been designed by the creator of the mod with a certain degree of raid difficulty from easy to hard.
The mod is really interesting because it takes the main feature of the game and implements it for PvE servers, allowing players that dislke the ideea of PvP to enjoy raiding and engage with the game in a more dynamic way. This can also be considered additional content for PvE servers.
After the creation of this mod, servers that use it have spiked in popularity and there is no doubt that this idea is very succesful.
I would consider this addition to be very fun on PvE and PvE-Conflict servers as it would get one of the features, raiding, to be experienced by PvE players as well.