I always thought in general the crime and punishment system was a little sketchy. a revamp of that would go a long way to "bring players together" creating a less hostile/ambiguous nature to player interaction.
I cannot provide a solution currently, but anything that promotes more positive social interaction like trading between cities or hermit players would be welcomed. Basically it would be nice to not assume every player is a cutthroat maniac who is going to vandalize, steal and or murder you, which I've found many players adopt this viewpoint after playing for a short time. Perhaps a factional alignment system, or overhaul to the criminal justice system in game. As is for newer players it is rather mysterious how it works, and honestly not very practical.
Anything that goes in the direction of creating a more rewarding interaction with others players over the current system provides is welcome. Both positive and negative interactions, via trade or crime.