Too bad this is a WL only mod. I love Crimson Skies, but I haven't got Warlords yet. I'm sure to give this a try when I can.
As to the Zeps, I always had an idea for a light patrol zep. It would be a small ship, stats equal to the light cargo zep, but faster (moves farther), and with no cargo. It would be used mainly for patroling your boarders. Not sure how relevent this might be. The airships have always been one of the most appealing things about CS for me. I love airships.
Have you figured out a way to make the AI use the zeps, or is this a MP only scenario?
One other thing on the zeps as trade inferstructer. Do you have Free Mind? I worked up an idea for a civilian derigible to simulate the great German Zeppelins. I think it would be implementable to some extent using just XML and Python, but I'm not sure. When I came up with it, I did not plan on using it for an actual goods trade unit, rather I designed it as a gold generator. Basically, it's a non-combat unit that can fly around the world, and everytime it enters a city, it generates an amount of gold based on several factors like distance traveled, nationality of the departure and arrival cities, and a few other things. Simulates a passenger travel service. I created a Free Mind Mind-Map for it, if your interested. I've never really looked into implementing it much, as with a lot of my mod ideas. I come up with a lot of ideas, but rarely ever put them into effect.
It might be possible to somehow rework the trade system in Civ into something more like Civ 1-2, where you actually built caravans that carried trade goods around the world. Maybe something where a city can build a load of a resource if it has access to the raw material. Then, that load is put on a transport and sent to another nation. That nation then has access to it for a certain number of turns, simulating using the load until it runs out. Not sure if this would be possible to do, let alone getting the AI to make use of it.
It might be nice if there were a way to use the above trade with the current system. You make a trade like you do now, but rather than being a transparent thing in the game, that trade agreement actually creates an AI controlled "caravan" that then navigates to the nearest city of the recieving nation. In CS, this caravan would be a light or medium Cargo Zep.
Building on that idea, would it be possible to have the game create random units. These would be passenger or cargo zeps that are not state owned that would randomly appear at a city and travel to another city, then disappear. Each city would get a bonus of some kind when a ship arrives or departs, and larger cities would create and attract more ships than smaller cities would. These would provide a target for pirates.
OK, I need to stop this post now. It's getting a bit long, sorry. I just love CS so much that I keep getting ideas for it. They may not be very good ideas, but I still get them.