I dont want spam of dead bodies on the maps, it would look silly. I also agree with Flippy, it would break the map designs if wrecks stayed too long. this is a game, it is about moving around and kill. the dead stuff should vanish like it does now. Just imagine dead bodies in a stair or doorway, you'd have bouncy, laggy, buggy collision problems and roads would be totally littered with wrecks. I think mapper-placed wrecks are better, as they are put there with intention, as cover.
It would take 10 sec in every assault map until the bottlenecks would be spammed with wrecks, just think Falaise Pocket bridge and what it would look like if wrecks stayed long.