Or, combined with the other idea to move the harvester; grain pirates! The small airship swoops down at night and picks up a some strip worth of grain, and is gone in the morning.

It is conceivable that unlike boats, autonomous airships may not need to be super big - they scale linearly. So a continuous swarm of small, lighter than air evacuated diamond foam devices could come, pick up stuff, and depart for local targets or far away targets via the jet stream. That also removes the need for the tower - they could pick stuff up right from the harvester.

I love it, this is really nice. Thank you!