I was thinking about the Diadem recently, and airships in general. I think they’re something of a missed opportunity. With Stormblood having come, I was thinking of a less temporal version of the Diadem, one that can be implemented using the most existing resources. These are my suggestions.
First, I’d like the airships to be more integral to the experience; at present they’re a gateway to the Diadem and an oversized retainer, which seems rather a waste. I would recommend that more equipment be added to them (we’ll get to why later). These would include weaponry, grappling lines, repair modules, pilot (your mammet), et al. Maybe even a sort of below-decks area that works like normal furnished housing so you can actually hang out on the ship (I’ll also recommend a docked airship as a housing style, but maybe later). At the very least, I think there should be a portal in your Company Workshop to the airship dock for that ship (an instance which would simply be an airship dock from the story mode with your airships on it, perhaps even other area’s docks as you dock them in “other nations”). The point being, the airships will be seen and equipment used, so how they function and look will be important.
Anyway, for these exploratory missions you will need to stock them with supplies. Dark matter for repairs, food to supply you, ammunition, essentially things your gatherers and crafters can be working on. I’d recommend enough that four people could, working hard, supply what you need in a night (with the goal being that it would be stretched out in people’s off-time over the course of a week). With an airship freed, and when the supplies are reached to your airship’s capacity, you can get an eight man full party together and start the exploratory mission (whatever it is called).
During the mission, you essentially jump from encounter to encounter in the airship. The typical encounter should be stopping at an island in the sky or sea. The island can be randomly sized, and might be several small islands that are joined by bridges, or one large complex island, etc. The weather can be random, and can utilize any weather from other areas, including some of the boss-specific weather). The airship you use will drop you off and may be docked or provide you air support (whichever is more appropriate, and maybe you can even leave some people on board to work the equipment to help out. What you find will be a toss-up though. A few examples:
Perhaps the island will be full of enemies, and killing them all will spawn a boss to kill (which might be a revisitation of an old boss reworked for an eight man, or a new boss, whatever works as more can be added later). Maybe the airship can provide artillery support on large add groups that the battle group might otherwise not be able to fight. Flying won’t be possible (the air currents are too strong for anything but a full airship) but you can use ground mounts.
Perhaps the island has a few enemies which can’t be killed and function as effective patrols. However, there are resource nodes on the island that can be visited in turn until they run out. Avoiding the patrols, killing the small number of enemies that you can kill, and gathering the resources would be the point of this island style. If you don’t have a particular crafter, you can summon your airship mammets to collect them as if they were players (at a reduced efficiency).
Perhaps you’re waylaid along the way. You may fight a reworked version of Bismarck from aboard your airship, using your grappling lines. Or you may come up against a Garlean airship, and need to fend off their boarding parties while using your guns to destroy key points on their ship (as well as keeping your own repaired with the aforementioned supplies) until you can board their airship. Or you may be set upon by pirates yourself and need to fend them off.