[manicpolymath]

This might be slow, but what about using the lift gas in a fuel cell with atmospheric O2 for extra efficiency? You reduce the lift gas in the bags, and if you store the water aboard then you get extra ballast. You could even “unload” the extra electricity for use groundside.

The corollary pipe dream here is to line the entire interior of the envelope as a fuel cell membrane and use the airship as a portable battery.

[m4rtink]

IIRC some military airships condensed water from their their engine exhaust to keep better control over their balance (the ship otherwise gets lighter as you burn fuel and you might have to release some of the irreplaceable lifting gas instead).