"Compressed air can be dangerous, but I have worked with high-pressure gases, and properly-designed filament-wound tanks can be punctured without exploding or fragmentation."

How about a hybrid? And use liquid air. Use small combustion motor to warm the liquid air. And have the high pressure of the air in a relatively small tank [somewhere between a CO2 cartridge and little propane tank]. If air is in a small tank you could have very high pressure with minor results if it explodes. And other some danger of your reserve freezing someone or something. And considering how much insulation you want wrap this in, there could little chance of rupturing it.
Plus filling liquid air could be less dangerous.