Some advice based on issues Ive encountered in the past:
The traffic cone function relies on the 'PickUp' command being on officers. Be sure as well to modify the script to assign/remove the approrpriate commands so the script functions properly.
For parking, you will need to modify the vehicle's collision box by going into the editor and then the physics section when editing the prototype. There you can define the size of the collision box so it is smaller than the actual vehicle. This helps in coaxing vehicles to park properly.
Regarding savegames, be aware that they are very easy to corrupt. Even changing one proto or model tends to bug it out. Scripts as well do harm to them, so savegames arent advisable to use due to their instability. If spawning is an issue, you will have to work on the spawn and toStation code to go around this issue. I wouldnt mind as well lending assistance to getting the spawn code working if its that much of an issue for the project.