This may be a good place to start.
On the vehicle side... no unfortunately. The pilot is not a negotiation it is a demand. For example the station will tell the vehicle you have 12A available. The vehicle must not exceed 12A. The vehicle side controller must communicate this to the on-board charger via some method.
The pilot from the charging station can also be dynamic, the station could initially give you a 30A pilot then reduce it to 15A then 6A if there is a power event or power capacity sharing. Again the vehicle MUST comply with the pilot. If there is no communication it would not be possible for the vehicle to reduce charging power on demand.
Proximity is a little different, the circuit is pretty simple. There are 3 states not connected, connected and connected with button pressed. All you need to do is ensure the vehicle on-board charger stops drawing current within 100ms of a button press.