Npcs that could live in your area… sweeping sidewalks, etc… attend parks with their pet, etc… purchasable from the cubit store as a “block” that when placed spawns the npc to live and wander within a set distance from spawn block.
Also animals for zoo… bonus:give us dinosaurs! 
I’ll buy an NPC if it can handle mall sign changes and portal sign changes for me
That would be nice.
But that’s probably not happening any time soon so…
Have you tried hidden locks for the signs? You could give perms to shop owners and let them change the signs by themselves
Thinking of some chores they could feasibly do… could be like the Farmhands in Farm Together, doing the chores within a certain radius of where you put them. Big ones I see: collecting crops, fueling portals, gather coin from plinths (send direct to your account), and killing critters. Maybe cut and plant grass options. Use tools you put in their inventory. I guess that could be a tough one though, suppose it would be like a bot citizen.
Could maybe even set to “Follow” mode, take them along with you. Set priorities (kill, gather: lustrous wood, gather: desert sword, ect), though they’ll stop and continue following once a certain distance away… also serve as a pack mule.