You are going to need to have a lot of things to do for it to appeal to the player.
Lots of diffrent jobs. You could have aircraft pilot to taxi driver. Police officer to FBI Agent.
Random odd events happening like weather that damages things (then you have jobs for people to repair and similar stuff).
I can see it being a lot of work though... I would recommend making this for Armed Assualt.
ALSO.. is this a MP or SP map.