For anyone trying to use land vehicles in their game, I realized there's a very simple way to get the same effect as the built-in vehicle feature without any scripting in just a couple event pages.
Page 1 is the idle vehicle without anyone driving it. Activating it plays a little animation of the player climbing inside, and then a self switch takes us to page 2, where we're behind the wheel.
Boarding the vehicle event makes it invisible, hides the players' followers and replaces the actor sprite with one of him driving the car. While the player drivers around, the invisible vehicle event remains glued to the player (make sure you set the autonomous movement like the picture and have 'through' enabled in page 2 for this to work). This is so that wherever the player decides to disembark, that car event is able to reappear in a parked state facing the same direction the player was moving.
For parking to work we add a conditional branch where if the [OK] button is pressed, the self switch that brought us to page 2 is turned off, allowing the car event to return to its normal state and changing the actor sprite back to walking on foot after a little disembark animation.
There's some smoke and mirrors going on, but the end result is virtually the same as the built-in vehicle system. Here's a gif of the vehicle event in action.