I think they should use airships as guild bases. There is a lot of great potential to flesh this idea out without getting overly technical. I think most people would like a guild headquarters but realize the limitations inherent in placing these structures in the physical world-- a problem shared with airships. I don't envision airships so much as a mode of transportation but as bases in the sky.
Already in Eorzea, we know that there is teleportation via aetheryte. So envision if you could teleport to your guild airship from any aetheryte crystal. The airship itself is tied directly to the guild. Just to hash out a few points:
Ownership: The airship is captained by the designated guild leader/leaders. The ship's upgrades are items that retain ownership with the member that added them. Hopefully if XIV uses a LS-like system, there will be more advanced options such as allowing multilevel hierarchies (more than just shell, sack, pearl-- e.g., co-owned shells), temporary status changes ("you're captain for 30 days or until I reclaim it"), and voting protocols (captain unless voted out) so that all of the guild power is not squarely and indisputably on whoever started the guild (unless that's the way they want to run their guild.)
Features: Access to features would vary based on what your guild position allowed, but general onboard features would be games, music, coffers/vending, maybe barracks and rooms, guild PVE airship fights (fighting airborn enemies that attack your ship), guild vs. guild airship contests (racing and combat minigames), and the ability to drop off all guild members at an area simultaneously (might not be too useful as it would likely just make the captain, for example, send all members on board to the aetheryte rather than everyone going there individually. Of course there could be special airship dropoffs as well.) Not an incredibly useful thing so much as a cool place to cavort with your friends.
Upgrades: All upgrades are items, and when an item is "given" to the airship, the player that gives the item retains ownership. If the player is ever removed, all of those items go with them. Large upgrades would require several items before they could be added. For example, adding barracks to your ship would cost a lot, but the captain might get "Barracks Blueprints" while each other member donates "2 Construction Lumber" and "1 Barracks Bed". Features like rooms would be scaled so that if someone does leave, it won't necessarily take away that feature until the items are replaced, though most features would cease function until all items were there. Some examples:
Card table- a place for members to play the trading card game that we probably won't get :c
Cid Mark II Engine- an upgraded engine that allows for higher ascent where more powerful foes can be found
Port Cannon- a cannon for use in PVE and PVP airship minigames, manned by one or two players
Bar- a room where players can purchased food, drink, and meds stocked by the guild at (potentially) discounted prices, and otherwise hang out
Karaoke stage- I'm just sayin', there are lots of possibilities.
Not all features are "upgrades," particularly cosmetic things. The ship captain can allow or disallow whichever items will be applied to the ship's status.
So that's a semi-brief look at my concept for Guild Airships. Suggestions/criticisms welcome.
Ok, now we're going to get slash fiction of Wint x Kachi somehere... rule 34 and all...
Never confuse your inference as the listener for an implication of the speaker.
Good games are subjective like good food is subjective. You're not going to seriously tell me that there's not a psychological basis for why pizza is great and lutefisk is revolting. The thing about subjectivity is that, as subjects go, humans actually have a great deal in common.