I think it would encourage workers if their number of arrests/heals/other job activities are kept tally. Maybe the players with the most arrests, heals and whatever else could be displayed on the FreshRP website. I think that the tally should be visible in the player's stats along with their other stats. Maybe when the player reaches a target number, they get a one-off bonus until their next target. The bonus could be a badge, job promotion or some extra money.
What do you think? I hope you like my idea.