I think the night time mobs would be awesome. Certainly adds a sense of the world being active and alive. I think the idea of camps as safe havens a nice idea too. Even add a night time NM to each zone that has a random spawn time after "X" hours of being defeated. This NM brings with it a bunch of adds or just a few stronger adds depending on if its a higher level zone or starter zone. Let them raid the camps until they're stopped, or just focus on one camp a night, "stealing" an NPC say the repair or merchant NPC, or maybe the crafting NPC. The only way to get them back is by killing the NM. If you miss the chance the first night then you gotta wait till the next night. If no one or no groups track and kill NM then NPC keep getting NPC-napped rendering the camps only useful in the most basic aspect (leves and teleporting). To still add a small motive (other than NPC rescue) have the NMs reward something decent but not over-the-top like a decent but still still kinda modest chunk of gil, or a unique crafting mat for a sweet item respective to the level of that zone/camp.