I believe the change must be made and keys implemented into the game.
I will respond to each comment by Eichi.
"My uniform disappeared, now my car keys are gone" (If you have experience this, please report it here) Fixes - Able to craft spare keys, vehicle unlock after x amount of days so vehicles can be reclaimed. My experience the last few weeks no clothing has been disappearing.
"I have locked my keys in my car" - Safe zones vehicles automatically unlock at restart, vehicle unlock x days ect
"My corpse de-spawned with my car keys in it" - this does not occur currently so why would it when keys are implemented.
"My friend wants to drive my car, but I am miles away with the keys with me" - ridiculous
"I have ten keys in my safe, but only three cars. Which one is still in use?" - pen and paper and half a brain will sort this out
The several changes suggested insted of the keys seem ok but if you're going to do all that just implement the keys!
Can i also mention that the thermal scanners are almost pointless. I think you have 15 min to scan a vehicle then after only three attempts at cracking the code you are locked out. Add to this that you may have just killed a player at their vehicle and you cannot take it? Not very realistic.
The major benefits of introducing keys are the PvP situations it can create and also adding some value into killing and or looting another player. Currently you loot a geared player and basically get nothing out of it as you can only carry one good primary weapon and most other items have little or no value.
All of you veterans of Arma 2 mods think of them times you pulled off a great shot on a passer by or you loot a guys body under heavy fire to obtain an enemy player's key then vehicle, it's a thrill and reward like nothing the exile mod currently has to offer. (fond memories of stealing btr's)
Mods please take notice, it was the most viewed thread on the new feature thread by a long way and for good reason, it's a major problem with the mod. For those who voted against the changes back to keys you need to have a good look at yourselves in the mirror and take off your sisters underwear.
In closing Arma should be a gripping and thrilling experience of towering highs and humiliating lows not the security of "ive locked my car"