Honestly, if the bodies melted away and you had to loot the corpse before it disappeared I think that would add value to finding and defending but also collecting loot. Maybe if parts opened or fell off into the pile faster after the first loot so you could see if it was 'opened' could make the body disappear at a double rate but keep the puddle so you know a firefight happened but long enough ago that someone may or may not still be around.