-Improved NPC behaviour. If you kill an NPC/Steal it should cause NPCs within a radius to rush to the nearest guard (even if the nearest guard is outside a building). Right now NPCs aren't too bright and you can easily avoid guards on their normal patrols
-One death and you get a clean slate seems a little light. Maybe if you killed multiple NPCs/stolen a lot you would earn up to 5 mins in a jail cell. You could even add a mini game of trying to pick the lock on your cell to escape the prison.
-Upgrade all guards of a city/town to the level of the Justice system guards. Seems strange only specific guards will confront you even though you've been listed as notorious/kill on sight.
-Kill on sight drops off a little too fast just by being outside the city for a small period of time.
-There's too many entrances to the Outlaw's den. Is this an Outlaw's den or a massive underground base located at every major city? I'd recommend reducing it to only one entrance in every city, if not completely removing them all and have a few dens that can be discovered outside of cities (hidden against a mountain somewhere, etc).
-Have a small arena in the Outlaw's den that allows people to duel. Also allow them and anyone else there to put wagers on fights.
Just some quick thoughts after checking it out.
"There is only one god, and his name is Death. And there is only one thing we say to Death: Not today." -Syrio Forel