I love Zeppelins. Not blimps. Airships. Rigid structure, an aerodynamic hull around a series of gas chambers. That sort of thing. Now for the past year or so my older son and I have sometimes dabbled in One Page Rules Grimdark Future FTL Warfleets. The rules are simple enough (two pages, not one, but one may argue that you can print double-sided). But it takes place in space. My son loves it. I like it too. But I feel one could do an airship mod.
Working on it. Of course.
Now airships _were_ used as weapons of war for a couple of years that included World War I. Afterwards there were some attempts to have them in a military role by the victorious powers. The USA built the USS Akon, which was a flying aircraft carrier – although more of a scouting vessel than made for direct sorties against hostile targets. I think the British and French also built them. Germany wasn't allowed the big toys anymore after the Treaty of Versailles so the greatest fans of the technology only built civilian airships.
A little aside on those: The Graf Zeppelin was the vessel which I personally would want to travel on if I ever got my hands on a time machine. Global readers will associate the term Zeppelin with the Hindenburg, however. It was known for two things: Having swastikas on its tailfins and spectacularly (and on camera!) going up in flames. Two things to save the honor of that airship: The Nazis didn't like Zeppelins because by that time airplanes were faster, more reliable and had more range than before and they thought the Zeppelin technology to be of no use for the military. The swastikas on the tailfins were not supposed to show how nazi the ship was but simply the national flag at the time. As for the fireball: The Hindenburg was designed to be run with (nonflammable) helium gas. But pre-war sanctions against Germany meant that the one big producer of helium at the time, the USA, didn't deliver that gas so they had to go with hydrogen, which has somewhat (8%) greater lift and far greater risk.
Alright, aside's over, let's talk about these hypothetical war Zeppelins. An airship is mostly gas-bags and the structure supporting them. The gondolas, both for command/control and with motors, are tiny attachments to that. Yet, an airship cannot carry all that much additional cargo/ammunition/personell. One cubic meter of helium only lifts something like 1.1 Kilogramms. That is not much and the reason, airships were so large.
So if we're gonna make a tabletop game out of this, we'd have to assume helium as lift-gas and ignore fire and loss of lift due to damage entirely. I dislike my games to be bogged down by to many detailed rules. Ships in Grimdark Future have between two (light) and four (heavy) ship systems. I'd go one lower for my airship mod because installing a cannon on such a craft is a big deal. Also, ships in the original game have turrets that become more powerful for the bigger craft. Airships will have a set of machine gun emplacements around their hull which means they all have the same base "turret" weaponry.
What weapons could one sensibly attach to an airship? Bombs (the most common weapon for such craft historically) are, of course, irrelevant in air-to-air battles. But there are other options:
Machine Gun Battery: If you expect to encounter lots of enemy planes trying to swarm you, this would be a sensible option. It simply means that there are _more_ machine guns on your ships - with the respective crews to fire them.
Anti Air Howitzer: I suppose an airship can carry a heavy infantry howitzer like mountain troops used to lug around. 150mm caliber, airburst-ammunition – this would be the king of weapons in the skies.
PomPom Battery: Heavier than machine guns, heavier than even heavy machine guns. The PomPom was a maxim machine gun upscaled to a 1-inch-caliber and did indeed see use as an anti-aircraft-weapon in WWI.
Dumbfire Rocket Rack: Just a bunch of rockets to saturate a distant area of the sky with explosions and shrapnell. The original game already has something like this which barely needs any modifications to work.
Wire Guided Missile System: This is the sniping weapon of the game, I guess. It could be made even though it is more of a WWII-kind of technology. We are doing Dieselpunk here so I guess it'll be alright.
3"-AA-Battery: This is the broadside-weapon in this system. Imagine like two cannons per side of the airship, firing smallish howitzer-rounds.
With weaponry out of the way, what ship systems would seem somewhat plausible?
Reinforced Structure: Your typical armour-upgrade. HP instead of anything actively useful.
Crew Parachutes: Good for morale if you play with such a thing.
Extra Motor Gondola: More speed!
Weapon Swivel-Mount: Choose one of your weapons. It can now turn 360 degrees. I imagine it's hanging below the ship.
Advanced Fire Control: Hit better.
Airplane Support Bays: Helps the swarms of fighters around you somehow.
Turret-Upgrade: Replaces the generic MGs with PomPoms?
Harpoon-Cannons: Entangle an enemy ship. This makes sense if you are smaller and want to hinder a larger craft from participating in the fight more.
This is missing rules for boarding, which I bemoan. I once met a nice oder lady at a lecture on airships who was not only leader of a club of Zeppelin-enthusiasts but also the granddaughter of Germanys only air corsair (the man had, in WWI, actually captured a Norwegian seagoing vessel with his airship). I believe that boarding may be unrealistic but is cool enough that it should be an option (in the base game as well - send over those space marines with boarding pods!). Have to think about it but I fear it would complicate things too much.