Hello,
to address multiple questions regarding new features, please find some hints below:
Checkpoint
Use LControl + B (default) to start. Aim at the car using the aim marker and keep aiming and then bring up the menu (left CAPSLOCK by default). A new option "Wave driver through" should appear and can be used to tell the currently selected driver to pass. You can also use another new command to tell him to stop. This is especially useful for cars behind the one you want to inspect in order to prevent them from overtaking when you arrest the driver in the car in front of them.
As for rotating, try holding down "CheckpointControlRotate" (default is LControlKey), this will allow you to rotate the vehicle. Also holding down LShift (hardcoded at the moment) will allow you more accurate placement.
Available keys:
Coffee
Hold down the key to sip - audio is very quiet and might only be heard in interiors.
Disable coffee:
Liveries
1.0c contains support for more than 4 liveries per vehicle ('>), simply add the textures to the .wtd file. Thanks especially to cp702 for his help.