Alright, since we're talking functions recently, here's a short layout of my conception for the "divide the police" plan that people keep coming back to. It's no abolishing capitalism, but I think it'd do fairly well and I hope it will help those of you skeptical of such a plan visualize it. All the organizations here would be separated to prevent esprit de corps from developing, and as it happens some of them are separated already!
Traffic & Parking Enforcement
Armament - NONE
Citation Powers - YES
Arrest Powers - NO
Mandatory Division - YES
Metermaids and traffic cops. No, they don't need arrest power and they certainly don't need guns. If someone doesn't pull over it's more dangerous for everybody to chase them, type their license plate into the system with dash photo attached and move on. Ticket will be mailed. Vehicular rampage to lethal threat response, license plate offenders to arrest & arraignment.
Drug & Substance Enforcement
ABOLISH
I could see the need for a force to, say, track down people making nerve gas. But people don't generally do that and the Feds are the ones who go after them when they do. People are growing weed and cooking meth, which should be addressed by decriminalization and social welfare programs. More LSD use could probably do our society some good anyway.
Fire & Building Code Enforcement
Armament - BATON & TAZER
Citation Powers - YES
Arrest Powers - NO
Mandatory Division - YES
Well, you know the Fire Marshals already, or you do if you've ever owned a commercial building. Honestly, I'd say of all the existing divided responsibilities these guys have the best enforcement-to-violence ratio. They're not squeaky clean, but they take their stuff seriously and I'd trade them with standard cops in a heartbeat. Some are currently allowed to carry guns and some aren't, I think that's a bit much but I also know how completely crazy some small business tyrants are about being regulated.
Hunting, Fishing, & Wildlife Enforcement
Armament - PISTOL & RIFLE
Citation Powers - YES
Arrest Powers - YES
Mandatory Division - NO IF URBAN COUNTY
Another pre-existing group, Rangers. And the first group I'm giving any actual guns, because grizzly bears do not respond to welfare programs. As with all divisions, this one would still only have enforcement powers within their area and scope, i.e., you can kick people out of the park for being drunk, but not cite them because they were drinking underage. Not that my fantasy law reforms use criminal charges to handle underage drinking. Anyway, people don't go around chanting "Fuck The Park Wardens" so I think minimal change is needed here. Might be nice to use them as a sort of EPA Police for wilderness areas, though.
Immigration & Customs Enforcement
ABOLISH
Undocumented immigration is an administrative affair and as unstoppable as drug use, seek green card reform not border walls. Also, probably prosecute everyone currently working for the federal ICE.
Investigation & Forensics
Armament - NONE
Citation Powers - NO
Arrest Powers - NO
Mandatory Division - YES
Maybe they'll actually investigate a house robbery or two like this. But I doubt it.
Arrest & Arraignment
Armament - TAZER & BATON STANDARD, PISTOL IF DANGEROUS
Citation Powers - NO
Arrest Powers - YES
Mandatory Division - YES
Behold, a pig! Or what's left of them. This group is here for a specific reason - to enforce arrest warrants. Ideally this will be minimal as the system will be designed to request appearance at court first, and only then issue a warrant. They would also perform lethal threat response if that division is not present in an area, though most such incidents seem to happen in cities or suburbs so this is less likely. If there is absolutely a need to guard an area, these guys and not LTR are the ones. Subject to increased penalties if convicted of a crime.
Lethal Threat Response
Armament - AUTOMATIC RIFLE, TAZER, & FLASHBANG
Citation Powers - NO
Arrest Powers - YES
Mandatory Division - NO
SWAT roles. To be deployed against mass shooter or siege incidents and certainly not for any kind of house raiding or riot response, let alone all the other bullshit existing SWAT are used for. Subject to military-style code of justice and increased penalties if convicted of a crime. I'm not entirely sure what to do with these fellows the 99% of the time they're not needed, maybe a reservist kind of thing with rotating shifts. If the firefighters can handle boredom, so can these.
Internal Affairs & Oversight
Armament - PISTOL (IA) / NONE (OS)
Citation Powers - COPS ONLY
Arrest Powers - COPS ONLY
Mandatory Division - YES
Behold, a metapig! Maybe they'll be not completely useless if they're not the same organization. Also, that's just the IA side. Oversight is of both IA and the other cops, and are either elected or appointed by the municipal government. Other people have written in detail how IA reforms and civilian oversight boards work, but as long as they actually do their job instead of following the thin blue line this is task accomplished. IA are subject to increased penalties if convicted of a crime.
Cybercrime
Armament - KEYBOARD & MOUSE
Citation Powers - NO
Arrest Powers - NO
Mandatory Division - NO
We do kind of need this, don't we? It might be better to get it out in the open, because any larger police department is definitely snooping through people's email and such already. I thought about this being part of an "anti-scam" group but then I remembered that scamming isn't strictly illegal.
Mental Welfare Services
Armament - NONE
Citation Powers - NO
Arrest Powers - NO
Mandatory Division - YES
No more fucking shooting people on "welfare checks". If you must have such things, it needs to be like this. Mental healthcare and crisis certification required, preferably based out of hospitals entirely. If you're thinking "but what if they're threatening to shoot themselves, that means they have a gun", I have never even once heard an EMT, therapist, or family member say they wanted the cops around in that scenario.
There's a whole host of legal and practice reforms that would have to go along with this sort of thing, and the existing cops would probably rather start a civil war than let it happen, but regardless I hope this is the kind of thing that helps understand what changes could be made in this fashion. This one doesn't take stretching the imagination that much to see it's probably better than the status quo.