Needs more collision. >:(
My reasoning is this: it's only going to really be good if you can walk around freely on the deck, in the same way as the GSF vehicles worked, as far as I know, and so the best way to do this is to remove the function of mounting the player to the vehicle, and improve the collision boxes, but I don't know how long that would take, or how difficult it would be. Also, I think that the only way to actually get to control the vehicle should be to click on the wheel, but I ask too much.
Good luck with it, but I'm not satisfied.