Great start-up question. Just of the top of my head:
Custom character creation for story mode
High stakes gambling in story mode
Street-boxing gambling with player participation
In-game custom journal
Some kind of further rewards for low-honor levels
Options to fence wagons/horses in other locations on the map
In depth Bounty hunting missions (as mentioned earlier-look in a general area, ask strangers etc.)--with an option to take payment from the bounty mark at the potential risk of becoming wanted yourself
More opportunities for your character to defuse/be arrested for the wanted level/bounty on their head.
An eventual refusal of the player paying his/her own bounty (maybe the station workers calling out for the police or something?). Eventually dead or alive has to mean something :)
Better/more dueling options.
Stop the homicidal deer/goat/moose near the cliff-edges.
Player-initiated pickpocketing
Obligatory Law Enforcement Mod 😎