For making more npc missions and adding a bit of rpg to the game I'd suggest having 3 organisations:
-Maffia: They will give you missions to bring item, talk to or steal item.
-Police/CIA: They will give you missions to do the same + intercept someone doing a maffia mission.
-Private detective: They will give you missions to find person or item, which are randomly located in the world. Kind of like a find wally thing.

The PD missions are neutral and award say x amount for zero risk.
The CIA missions are positive and award say 1,5x amount for small risk of mission failing.
The maffia missions are negative and award say 2-3x amount for medium risk.

Doing maffia or CIA missions will unlock more missions of that kind and lower the missions you can do with the other.

2 cool examples:
EXAMPLE A
-Maffia mission: take this cheating device and go play in James Tower and win double at slots, come back with 1k chips.
-Guard job or CIA mission: We have information about people trying to cheat our slots with a device, come back with the device.

This would make it interesting to do guard job or have a 2 player mission. The game aspect would bethat you see a person at slots and occasionally you see something above their head like exclamation mark. The guard needs to click this to "catch" the cheater. Which completes your mission, but fails the maffia mission.

EXAMPLE B
-Maffia mission: Bring this item to person x
-CIA mission: We have information of an item being handed to person x, intercept the transport.

Again a 2 player mission, or if no 2 players, an npc could do the other part.
Here the maffia guy walks towards to contact location. The CIA guy has to find the person walking, which is indicated occasionally by exclamation mark above the head. Clicking it finishes CIA mission, but fails maffia mission.

If you are interested, I can talk about it some more in chat or something :)