For maximum play value at a certain piece count / price point, I think they might represent the zeppelin with just the passenger compartment and ignore the rest of it, since it'd be just a bunch of bricks assembled into a huge structure that would inflate the cost of the set without actually adding a lot of play features. Fans interested in more fully representing the entire structure could always fill in the rest with bricks from their own parts inventories if interested.
I could see Marcus being in the Venice chase set, since he is at least in Venice in the movie, not too far away from the chase when it takes place, and licensees have often played around with the factual particulars of a scene in order to get a certain desired play value or whatever out of a toy. LEGO's own Well of the Souls set (Indiana Jones and the Lost Tomb) includes both Marion and the Ark of the Covenant, even though the Ark had been lifted out by the time Marion was thrown in in the movie (if there'd been a Sallah minifig in the set, it would've been ideal for representing all the scenes in the Well from the time Indy first descends into it to the moment he breaks through the wall with the statue), and of course lots of the KotCS sets take all sorts of liberties with the narrative (presumably at least in part because the movie was still being made as the sets were designed, and things changed along the way, but other aspects simply combine different scenes into sets to get the most mileage out of a set, for example).
At any rate, we'll see what's in the new sets soon enough, and assuming the line continues to do well, it might go a few more years, in which case I think we'll get lots more stuff from all four movies represented in various sets. They might well even redo certain scenes, locales, vehicles, etc., just as they have with their other Lucasfilm license.
