One very annoying visual bug related to vehicles is that any equipment worn by characters entering a car will clip through car seats (backpacks) and the roof of the car (rifles, nightvision and other things protruding above the player's head. Long rifles (Mosin/SVD ) are especially notorious for this, but most weapons do it.)
I suggest doing one of two things:
# **The complicated way** - add attachment proxies in the boot of cars where up to four backpacks can be attached (=visually put in the boot) and make it impossible to enter a vehicle while wearing a backpack. Same with items worn in shoulder slots, it would be impossible to enter the car with items still in these slots. The items would need to be held in hands (one item) or put in the boot. This would be realistic and fit well in DayZ.
# **The simple way** - simply **hide** any piece of equipment worn by characters in the shoulder and backpack slots when sitting in a vehicle. This would of course be unrealistic and not very DayZ-ish (but so is backpacks and rifles protruding through car seats and roofs) but likely involve lesser development time. You already do this with items held in a character's hands so it should be simple enough.
Oh about that - please make it impossible to enter vehices (at the very least as driver!) with barrels, wheels or other bulky (the slow walk animation stuff) in hands. It is just too cheezy that a barrel can magically be sent into some parallell dimension when you get into a car...