Modern Elmo hits the nail on the head with <<In regard to the helium problem: the only airship proposals I can take seriously are ones which don't require helium to be dumped in order to descend and land.>>
The obvious advantage of airships is that the aircraft itself can be neutrally buoyant - needing no power other than a little for trim, altitude change, and modest speed - the catch is the weight of fuel to be consumed in a flight and that anything other than relatively (to the aircraft itself) insignificant payloads are carried - heavy payloads would require a lot of thrust (and therefore fuel) to lift or unload or large adjustment of gas (dumping or compression, both I would suggest impractical).
The Zeppelins carried (correct me if I'm wrong) a small mass of passengers relative to the mass of the airship, from prepared point to prepared point, and used readily available hydrogen. They would be very vulnerable to adverse weather (eg icing R101 - can you imagine de-icing kit for a large airship?).
Moving hundreds of tons to FAFs - I don't think so.
Long range recce (a role with fixed payload) at modest speed - definitely.
Another investor con, I reckon.