The end of the easy joyride
In GTA 5, if you saw a cool supercar parked on the street, you just smashed the window and drove off in two seconds. It was fun, but not exactly realistic. The early development leaks showed Jason and Lucia using an actual inventory system that held dedicated burglary tools.
This completely changes the game. If you try to smash the window of a luxury sports car now, the alarm is going to go crazy. Everyone on the street will look at you, and the cops will get called immediately. It is going to force you to actually think before you steal.
The tools you will need
From what we can tell so far, there are going to be a few different ways to boost a ride.
The old fashioned brute force way still exists. You can smash the window, but it is loud and messy. Great for emergencies, terrible for stealth.
For older cars, you will probably need a slim jim or a lockpick. It takes a few extra seconds and you might have to play a quick mini game to unlock the door, but it keeps things quiet.
The really interesting part is the modern cars. High end vehicles have electronic immobilizers. You can't just cross two wires to start them. You will likely have to buy expensive hacking devices from the black market that spoof the key fob signal so you can drive away without triggering the massive alarm system.
Risk and reward
I love this change because it adds so much tension. If your getaway car blows up during a bank heist, you can't just grab the nearest passing Ferrari unless you remembered to bring your hacking tool. You might have to settle for stealing a beat up old delivery truck because it is the only thing you can start manually before the cops arrive.