If you want armored airships, go for a zeppelin base(rigid balloon) and build the rest of the airship on the outside of the balloon.In fact you could have some hallways pass through the balloon. To keep a battle away from one shot and done, compartmentalize the balloon.Even if it's hit you don't lose the whole bag, just the damaged sections.
Now guns aren't going to be big. In fact the largest gun on a airship will be the size of the boarding cannons on a naval ship. Able to be carried by one or two persons. Why? Recoil! A navy vessel can be overturned by firing it's larger guns, and your airship is lighter, and doesn't have the water to help absorb the impact so a large gun will not work. and reason number two works into the next consideration....
WEIGHT! Your Ariel Navy is going to be NASA level obsessed about weight. Every crewman, gun, uniform, utensil, bullet, tack, etc... will be weighed, and accounted for, and depending on mission requirements could even lead to crew being left behind or swapped out because they put a little on.
Crew: your looking at about 40 people for a "small" vessel. Captain, CO, Dedicated back-up pilot, dedicated comm, dedicated navigator, Back ups for each position, Engineer, 6 mechanics to cover shifts, Doctor, and at least 2 assistants, Dedicated support staff including Cook, aides for officers, Bosun or Quartermaster, Gunnery crew(at least 2 for each gun) and a gunnery chief, plus Midshipmen out the wazoo. Midshipmen would be underage children that act as gofers, and extra hands for maintenance, as well as lookouts since your captain isn't going to have a complete view of the area around his ship.(The bag at least will get in the way, especially if he's piloting from the back(as you suggested) which would really be more of a Command position.
OH! and Marines. The Marines would be your "ground forces" as well as your boarding parties. Figure 2 6 man rifle squads and a CO of their own. And while they are on your ship they ARE NOT part of the Navy ,and don't count as part of the 40 man number above,and have their own bunks, and areas. They will probably be trained to back up your gunners, and repel boarders, and act as MPs on board.
One of the reasons that it's so much fun writing airships is how big they are. My transdimensional (Oh, and I wrote it well before the Baxter/Pratchett long earth books) one is over a kilometre in length
Now for a different topic. I've been wondering about what effect an aerial navy would have on ground forces. Basically, would aerial navies such as this make standing armies obsolete?
And of course, the more weather magic you have...
If they can't control the weather, how well can they predict when the winds and clouds are coming, or even interfere with each other's probes of it? And that's the kind of hidden power that would let any side could keep someone around that gives them an edge without publicly admitting they're using magic-- which is how governments usually use "forbidden weapons."
And even then, if an occultist was that powerful, they probably couldn't care less about politics or wars and would feel no loyalty to anything other than the Occult. And then of course the governments themselves would have to trust an occultists, which I doubt any but the most determined (or forward thinking) could bring themselves to. The fear and hatred of magic runs deep in society.
Basic Illusions and subtle mind manipulation would wreak havoc on an army or another airship Captain/pilot. Heat of the battle, and he exposes his flank to a broadside, or empties his pistol into his own crew? Not to mention the occultists don't have to be willing participants. Just look at all the horrible things our government did to it's own citizens trying to get a slight advantage over the Russians, and all of a sudden those arrested occultists are training special liaison agents that are there to "observe" the battles....