I think they should just increase the amount they have to pay. Maybe half of what the car is worth and for those who don't have money to pay the game should take assests like weapons and ammo starting with the big weapons first. Another thing they could do if they don't have the money to pay is repo their cars.
Personally I don't care if someone blows up my car. My problem is ppl are able to do it with no real punishment so the game becomes a bomb fest. I'd rather ppl try to kill each other by shooting bcuz its more challenging instead of using the easy route which is stickies and RPGs.