A suggestion.
Police shall not be demoted. Ever.
However, a karma system shall be used.
Each policeman's rank is determined by karma, not by it's criminal status etc.
Lower the karma, lower the policeman gets. Bigger the karma, bigger the rewards.
To addition to the next list, each 25 Karma decreases/increases salary by $10. Meaning that if a policeman starts at 100 Karma, he gets just $40 paycheck. However, jailing someone grants you Karma (And money, also based on karma, if the criminals still work with granted levels. [Exemplified with 100 Karma]. 1 star criminal jailed: 100*1/2 = $50. 6 star criminal jailed: 100*6/2 = $300. [Exemplified with 200 Karma]. 1 star criminal jailed: 200*1/2 = $100, and so on.) based on.. Karma! Having Karma under 50 decreases your Karma gains a lot, that way people will have a hard time getting back on their feet (5 Karma a jail) if they screw up.
Karma table (details would normally be hidden from the user):
[Killing a innocent at any rank except Corrupted and Retired removes 15 Karma]
Wanted: <-150 Karma: Nothing | No way to add to karma, can be jailed the same way as criminal leader.
Corrupted: <50 Karma: "Limited" Baton | 5 Karma / Jail | -25 Karma / Killed innocent
Retired: 50 - 75 Karma: Baton | 15 Karma / Jail | -20 Karma / Killed innocent
Cadet: 75 - 150 Karma: Baton , Stun pistol | 20 Karma / Jail
Policeman: 150 - 250 Karma: Baton, Stun pistol , Pistol | 20 Karma / Jail
Scout: 250 - 400 Karma: Baton, Stun pistol , More powerful Pistol | 15 Karma / Jail
Longrage: 400 - 500 Karma: Baton, Stun rifle , More powerful Pistol | 15 Karma / Jail
Longrage Special Ops.: 500 - 700 Karma: Baton, Stun rifle , Stun grenade , More powerful pistol | 15 Karma / Jail
After this jailing is limited to criminals with wanted level 2 or more.
Special Ops.: 700 - 1000 Karma: Baton, Stun shotgun , Submachine gun | 10 Karma / Jail
Raid Tactical Division: 1000 - 1500 Karma: Baton, Stun shotgun, Stun grenade, More powerful SMG, Shotgun | 20 Karma / Jail
Oversight: 1500 - 1700 Karma: Baton, Stun shotgun, More powerful pistol, One hit kill sniper | 50 Karma / Jail
Recon Tactical Divisoin: 1700> Karma: Baton, Stun grenade, More powerful SMG, More powerful Shotgun, Explosives of any kind | 5 Karma / Jail
Same could be done to other jobs. Reffering to criminals, bigger Karma means better weapons. Reffering to other jobs, bigger Karma means less resource usage (Shopkeepers?) and/or better salary. Eventually having a specified number of more (/less) karma would mean buffs/debuffs. Like, builders normally can have 3 lots (?). Them earning karma would be done by building. Having 4000 Karma (1667 bricks a lot [?]) would mean they can have 2 more lots. Or something of the same kind.
To prevent high ranks going rampages on everyone without worrying about going Wanted: Losing 400 Karma in 2 real life hour means a 1 in-game month suspension to Retired, with no way to build Karma back up. After the suspension the user is 2 ranks below the suspension. (Being Recon Tactical Devision and getting a suspension would mean that after the suspension you'd be Raid Tactical Division).
Other words, this suggestion is Karma.