Not impractical really, according to Wikipedia even the old Hindenburg: "held 200,000 cubic metres (7,062,000 cu ft) of gas in 16 bags or cells with a useful lift of approximately 232 t (511,000 lb). This provided a margin above the 215 t (474,000 lb) average gross weight of the ship with fuel, equipment, 10,000 kg (22,000 lb) of mail and cargo, about 90 passengers and crew and their luggage."
So if it has a capacity of 40,000+ lb beyond all the needed crew, passengers, fuel, and whatever cargo with a 100 year old design using diesel engines I imagine you throw a small nuclear reactor for power in a modern design you could probably float around for a while with some pretty comfy accomodations.
Thus the 'aside from launch failure's part. No rocket scientist here, but way I figure if we can send probes to do flyby photos of the outer planets how hard can it be to hit the biggest thing in our system?
Lift costs might be stupidly high too, but more a would it be possible thought.