I recall one past proposal was a “flying wing” layout ala Jack Northrup's pioneering designs. (Which weren't original to him, BTW, as two German brothers did seminal work on the concept during WW2, with at least one example a pile of parts at USAF’s Wright-Pat museum last time I was there.)
Frankly, from a pilot's standpoint, I don't see the practicality. Basically all that's being accomplished is a reduction in the aircraft's empty weight - which still has to be negative bouyancy with the aircraft defueled and unloaded or you face even greater control/movement hurdles - and to gain this you have to “give up” a lot of wetted area as a aerodynamic drag penalty which increases your power requirements, hence effecting fuel burn, which increases the basic weight, which reduces cargo load. And so it goes......
Alas, in aviation there's no such thing as a “free lunch”. Every aircraft design past, present and future, is a hodgepodge of compromises decided based upon specifications for weight, range, speed, handling characteristics, operating environment and a host of other criteria. “Getting” something means “giving” something somewhere else in the performance envelope. We already have a host of HTA “heavy lifter” designs in production, not to mention some very interesting “Superlift” WIGE point designs sitting in airparks.
Sorry, I don't see the concept as having much practical/economic application. If it did, it would be flying right now. >PS
There is a bright future for the “ Big Gas Bags” look how many have been floating around Washington for years and years.