> Everything else on board for propulsion and housing the pilot would be on the scale of a small prop aircraft
It's likely that any cargo airship would fly for days/weeks at a time and would require at least 4 crew-members and everything they would need for the length of the voyage. So less a small prop and more something akin to facilities available on a yacht/Large RV.
> You might not even need pilots since these would be perfect targets for automation.
This would perhaps be the best solution
As for speed, you can optimize the shape of the aircraft and the position of the propeller for this. I've seen a number of videos that show surprisingly good performance for pointier fuselage with a pusher prop on the tail.