The same way owned cars don't despawn, we should make it so that any car that a player has keys for should not despawn. It's frustrating to be doing shady things, using a stolen car, and you go inside somewhere or walk away too far and the car despawns, stranding you in the middle of nowhere, having to steal a car and alerting authorities.
This would also create an environment where players can be more creative with getaways, planning their escape more elaboratively, allowing for much more variety other than just losing sight of the cops. You could plant cars in planned spots, I've even seen situations where the police find the cars in advance and hide in the trunk, allowing for the car to be tracked by police, or the classic block-the-tunnel and have another car parked ahead that crims can swap to! This would open up for a lot more roleplay opportunity, creative police chases, and cut down on the current uselessness of stolen cars. It would be a great QOL addition to the server!