The AEMS Guidebook I feel is a good place to start as it has a basic framework to it, which can be added on and expanded upon easily.
As far as making this viable... I wouldn't say completely remove defibs, but make them less accessible. Make them so they can only be bought at the Kavala Hospital or Georgetown hospital. Make it so defibs can not be stored at houses (to avoid the inevitable pile up of them at houses). Keep the NPC medics in the town, however make it so that they can only sell basic medical supplies such as FAKs and maybe adrenaline (and medical marijuana of course). Keep the ability for the NPC medic to be able to heal. Blood Bags and Splints should be restricted to medically trained personnel only (EMT slots, and APD medic slots). Those are a couple things to change the mechanics and keep it somewhat fair, I would think.
Ranks for white-listed medics should be simple and more then likely follow the APD type of rank structure to allow for advancement and such, though if it is a bit much on the ranks there are places it can be skimmed easily without losing its core structure:
EMS Chief or Chief Medical Officer (Chief) *EMS Staff Rank*
EMS Captain (Captain) *EMS Staff Rank*
EMS Lieutenant (Lieutenant) *EMS Staff Rank*
EMS Supervisor or Supervisory EMT/Paramedic (Sergeant) *EMS Staff Rank*
Paramedic (Corporal)
Emergency Medical Technician (Constable)
Emergency Medical Technician Recruit (Recruit)
Volunteer Medic (Un-whitelisted Medics)
Un-whitelisted Medics should be restricted in the abilities they are able to perform, to maintain a value to the white-listed spots. My suggestions on this would be that they should not be able to use the defib or adrenaline shot, their bloodbags remain restricted at 50%, and they have full access to use the splint, taxi requests, and repairing vehicles. Their vehicle selection would also remain restricted to the Offroad only.
Whitelisted medics should maintain the relatively same talent tree that exists now as it does work out fairly well. Offroad, SUV and Hummingbird should be included as a base vehicle set for white-listed medics, with Hatchback sport achievable at (following the rank guide above) Paramedic, maybe at EMT if it is absolutely necessary or not a real problem overall. Add in at least the hellcat as an additional helicopter for Paramedic and above, and possibly the Orca for EMT Staff positions though an Orca wouldn't completely be necessary to the EMS division personally.
Payouts definitely need some sort of boost. 800 dollars for a revive is pretty shoddy at best. I know taxi system was revamped a bit with payout, but realistically how used is the taxi service to begin with? Base award received from revive on distance, with base payout being 1500 dollars. With this, Civs and APD would pay half of the cost and let "insurance" or the government stipends make up the other half. Taxi service payout is fine as it is, even though rarely used. Other actions such as performing a blood bag, splint, adrenaline shot, and repairing vehicles should payout something, since it takes the medics time and he is actually doing something for the populace, though these action should payout less then the base revival pay of 1500 as stated above.
And then you got your basic rules and such which would be hashed out behind closed doors more then likely, but as people have said before, the EMTs should remain unbiased, attempting to save and attend to any person's life, whether its APD, civilian or rebel.
If I can think of more, I'll add it but this would be a good start at least.
