When you are already in a car, it would be nice to have a small indicator at the bottom left/right, such as a small green circle which means the car is unlocked. This circle is replaced with the red one once the car is locked. Make it visible for passengers too. Don't make the circles big.
I feel it's necessary because you may not always be sure if you are driving with the doors locked or not, especially when you want to quickly rob someone, which makes the people easily jack you out of the car. When you want to pick someone up, you have to type /lk twice sometimes if you are unsure if the car is locked or not which isn't ideal, considering the annoying "Please wait before sending another command" msg sometimes.
