An opponent's unit may move onto or through your airship's territory only if it's transporting resources.
This is saying that the opponent's unit has to be transporting resources to move to my airship, not that opponents can't go near my empty airship, right?
Yeah, the opponent's unit.
Another question established that an airship can pick up resources from an uncontrolled hex. What about a contested hex (in which a combat is pending)? If I carry resources into a battle as an attacker, can I have my airship come in and pick them up with a subsequent move? (I'm guessing not, but if so, there's a follow-up question about whether you can immediately restock an airship's resources after spending them on Bombard/Espionage/Bounty since you're still in the middle of resolving a Move action.)
I think the territory needs to be uncontrolled or controlled by you. Control changes would happen after combat, which is after all moves happen (note, not displacing workers).
Blitzkrieg creates an airship-only combat. Does this resolve immediately or does it wait for the end of all movements like normal combats? If it waits for the usual combats, does the airship combat happen before or after ground combats? (The former matters for several movement-affecting airship passives, the latter I can only come up with a case where it matters if you're playing with individual airship abilities and you have blitzkrieg vs another combat ability.)
Same as other combat, after movement. Attacker picks the order as always.
Hero: never paid attention to this much in the base game rules, but after a non-Saxony player fulfills an objective, they're still holding their second objective and can cycle through it with Hero as much as they want, right? Can you declare your airship to be one of your movements but not actually move it, to trigger Hero?
You have to physically move it, but it can move off and back on if you have moves more than 1. Spending 0 on a move is not allowed, a nett move of 0 is allowed.
Deja Vu: what does "accessible" mean?
Some of the encounter tokens can't be reached depending on which factions are in play, Due to their riverwalk and other special abilities. Those dead areas aren't counted.