I think a nemesis system as implemented in Shadows of Mordor wouldn't work for the new Fallout. But an adapted nemesis system could. Rather than characters you killed coming back to seek revenge, how about characters you've wronged in some way? For example stealing from them, ruining there reputation, killing a family member. They will then seek revenge based on a number of possibilities. (Depending on how you've wronged them and your general reputation)
1)Hire mobsters to wipe you out
2)Frame you for a crime
3)Steal there stuff back + yours
The possibilities are endless, you could go pretty deep with this.
1)Hire mobsters to wipe you out
2)Frame you for a crime
3)Steal there stuff back + yours
The possibilities are endless, you could go pretty deep with this.