5. Multiple gas cans in a single vehicle are much more likely to reach that ratio, and over a larger area as well.
This is where we disagree. The probability of a gas can's fuel-air ratio being ideal for ignition is exactly the same whether that gas can is next to another one or not. So although the probability of that specific vehicle catching fire is twenty times higher if it has twenty gas cans, the company that owns the vehicle has exactly the same chance of having a vehicle catch fire, because the probability does not decrease by adding more vehicles; it merely gets spread out over a larger number of death traps^H^H^H^H^H^H^H^H^H^H^Hvehicles.
6. A 10 gallon fuel fire is bad enough, a 200 gallon fuel fire is quite another. Note, I'm not including the vehicle's fuel tank because, on consideration, it's generally pretty well protected.
I was assuming more like a few 5-gallon cans per vehicle—say 25 to 30 gallons in total. Two-hundred gallons would be insane. A typical half-ton pickup can't even carry that much weight; that would exceed its maximum bed weight by about 250 pounds, not counting the gasoline tanks. Besides, tanks over 25 gallons have lots of additional regulations, and most cities' fire codes won't let you store more than 25-30 gasoline cans in a single home or business, so if you go over that limit, you'd never be able to legally park the vehicle overnight....