fundamental design flaw
if the motors and fuel tanks had been arranged for easy jettisoning the weight reduction would lift the envelope and passenger cell away from the fire.
Of course you then have the problem of getting back down again - you'd either have to have a preplanned helium venting procedure, or else a recovery parachute system
n this particular case you could do the reverse: if the passenger cell had also been fitted with a quick release then the envelope would have lifted taking the motors and fuel away from the crew
either way, its do-able as long as the passenger cell is separate from the propulsion systems