I'd like to add more NPC's to my world, so that it's not an deserted place when I visit for short periods.
Adding one of my characters is great for testing out my placement of sex objects, but they don't wander off and do anything on their own. (and even if they did... just 2 of them... I'd have to intentionally have to go looking for them).
Interacting with other real people is great and all, but making new friends is time consuming especially when I'm just looking for a brief encounter (which is also possible with real people) but an NPC would also give me/the user more control over the interaction.
I think it would add to the experience if I could add a dozen, even if randomly designed, male or female NPC's. That either randomly walk around my environment, interacting with the sex objects or that I place in specific locations myself.... that you can interact with.