Re: Small steps...
At last! A sensible discussion starts to take place.
(1) Yes, hybrid airships are already in use. A deltoid wing filled with, say, hydrogen that can generate contributory lift under forward propulsion, though air resistance becomes an issue. It's not going to be a direct competitor for the speedier traditional aircraft, but it would be faster than a ferry crossing - maybe the same speed as a rail crossing to Europe, but with a greater range of destinations. What about the use of aerogels filled with He/H? Create a rigid structure that's buoyant using that. Aircraft designers are already designing very lightweight fuselages through the use of carbon fibre composites, so technology advances.
(2) The hybrid engine sounds like a possibility, though they do mention that they wish to reduce the drag of an underslung engine. Possibly the old tri-star configuration could work - a tail mounted single jet engine with electrical engines in the wing root. Ground assisted take-off is another possibility, though that could require considerable alteration to runways which would be expensive.
(3) Yes, it is a battery, but what about some biomimetic technology to generate "artificial petrol"? That could be along in a few decades - using just as a guess say, sunlight directly to knock electrons off molecules, triggering the formation of less stable complex compounds. Developments in other areas of battery technology may produce a "liquid battery", unsuited as a replacement for the pastes, gels and powders of current batteries, but usable in cars, trains, even planes.
Be interesting to see what technologies develop from this.