As for the Prison/Jail separation concept, I think this is a great idea and we'll have to give it a try, test it, and see how it goes!
Concerning how Jail currently works though, killing people and committing high-level crimes is very punishable and not nerfed in any way. IE: For one murder you can serve up to 10 minutes in Jail. (With your idea of Prison/Jail separation, said murderer would rot in Prison instead of Jail. Prison would be harder to break out of [?])
If you're serious about the seperation of jail and prison, I would like to suggest something, and I think you'll like it:
BAIL BONDSMEN - Jail sucks. But if you got money, you can buy your way out. How? A bail bondsmen. As a jail-bird, you cannot make transactions yourself, so you have to sign a waver that basically says "I'll pay you $$$, and you pay $ to get me out of prison AKA my bail." It's expensive, but it could be less expensive than spending 4 hours in jail printing license plates.
Can be implemented. I've been to my local state jail (it was a school field trip for our law and justice honors class), it's brand new. If you ever played on the Brighter Dark's Jail escape, it's basically that.
Differences between jail and prison:
JAIL - within urban area, light security, no sniper towers, no tanks, no dogs, prisoners are ALLOWED to leave their cell for certain amounts of time (for our purposes, they can leave their cell indefinitely, unless a guard forces them back in to subdue a riot?), prisoners can engage in programs (music clubs, physical training, religious groups, etc), they can have basic possessions (books, magazines, pictures, etc), sometimes guards will give them distractions to prevent riots/mischief (let the prisoners play Xbox, I am completely serious.)
PRISON - forget life, you are going to die in here. Don't drop the soap? Prison. This is where the big bad wolf would go, if he were a heroin-dealing-child-molesting-quadruple-murder-sociopath. Prisoners are on lockdown at all times, and only given one hour for outside activity, which often times they are restrained and guarded. There are sniper towers, there are armored vehicles (SWAT), there is high level security, you forget up here, you DIE. You are out in the middle of nowhere (In our case, on an island, deep in the forest, in the mountains, etc.) VERY difficult to break out of without alarms sounding and guards running around with high powered weapons.
Vaux respond to my message please, it has actual questions in it that are important.
Also, my dad has a tendency of taking my computer to game, so most week days I don't have good odds of getting on, weekends are best days for me to work on the build.