FFXIV should take a note from SUIKODEN

[Saseal]

Ahhh!! Suikodennnn! I love those games!!

YESSSS *Raises the Jowston Alliance flag*

or hells. *Raises the Merc group Bear.... Lion.... flag.... thing*

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Fair warning, a shitload of TL;DR -

Honestly, it would be nice, but there would be too much data in customization. I also think it would be messing with the storyline that they're crafting if you have NPCs moving in. If younotice, the NPCs move around depending on the part of the story you're on. One moment, Thancred, Yshtola and the others are hanging out - his another plot point in the story and they're gone or standing about elsewhere. Same with the more minor peeps like Haory and his buddy. I also wouldn't want to see multiple NPCs in random places - it kind of breaks immersion. I was finding myself looking for the guys in the Rising Stones/Waking Sands throughout the storyline and seeing where they moved to and said in relation to the events unfolding or have happened. It's subtle, but amusing. Also, you would have about a million Thancreds, Yshtolas and so on all over the place. Same with minor characters like Haory. As much as I'd want to horde some NPCs for something like my own castle, I don't think it's a good idea in immersion terms.
On the same vibe, I don't want to walk into some other player's castle to talk to NPCs I need. It still breaks storyline.

If the OP means a castle owned by ALL players, and not a single person (as in, having a large collaborative fight to free a stronghold, and not one FC or person will own it - just become a free agent castle that the NPCs techncially run.... thats different. That would have to be written into thier storyline.
Something like this could be a story trial or a weekly event. NPC run castle attacked by x enemy forces and needs the adventurers help defending (or raiding).

Which reminds me, I should try to find some of those other peeps after 3.5's storyline (trying not to give spoilers...) and see if SE snuck them in the background of some location.

As for the castles, if refering to multiple of them.... another option I'd love to have, but this is technically fulfilled by the housing.

In terms of freeing and occupying a castle that an FC or person would own - RO does something like this with the War of Emperium event every week. I'd only taken part in the earlier days of WoE with one of the major guilds so I don't know if it's changed much... - but, basically, there are territories of maps with several castles on the map. During the allotted WoE time period (2 hours on a set day if I remember correctly), the map you're transferred to once stepping in the 'door' to the castle is an entirely PVP map.
You have the current owners of the castle - and their alliance guilds - set up to defend their Emperium crystal at the center of the castle (which consist of several rooms and some are quite maze-like if you don't know the route) from both the 'courtyard' area (hunters traps, etc) or castle walls (snipers/wizzes, etc) and then the REAL test of defense in the emperium room itself.
Then, the invading guilds and their alliances trying to get through the defenses (Send in the vit tanks to rush the defenses, follow it up with FS vit priests, etc) and DPS down the giant Emperium. Once the Emperium is broken, the old castle owners are punted out and the new guild has to set up defenses (then the old owners can try to take it back) asap.
The catch and similarity is in the win - the guild who holds the castle by the end of the 2 hours owns the castle for the week and can reap the benefits of the guild treasure, economy and place to chill - as well as access to the castle dungeon (which only allows access to the occupying guild and alliances). Main towns in the regions (Payon, Prontera, Geffen, etc) display flags with the guild logos/names for which owns castles.
Then it starts all over again next week and guilds fight guilds for the castle and it's benefits.

Unfortunately, except for some unwanted castles, smaller guilds never stood a chance in hell other than to get slaughtered by either the defenders, or bigger guilds attempting to raid the same castle (getting rid of competition... or just blood lust. "You're not our guild/alliance! KILL!*Smash*").
Heaven save the newbies wandering into the castle area out of curiousity and confusion.

if you're thinking about doing something like that but against, say NPC forces (Garlean or otherwise), there could only be so many castles to be occupied before there aren't any left for anyone else. And just like in RO, it's only going to be the super big FCs and hardcore FCs that will get any of them.

Though, I will say, having experience raiding a castle with a larger guild - it is quite fun >.> .....but only if you know the right people/FC.

[PlumpyMcduff]

Honestly, it would be nice, but there would be too much data in customization. I also think it would be messing with the storyline that they're crafting if you have NPCs moving in. If you notice, the NPCs move around depending on the part of the story you're on...

If done in a fashion where changes/unlock progress with the story, much of the data would be client-side. As for messing with the storyline, just like Suikoden, characters would come & go as the story continues (e.g. Cid leaves for a mission, is replaced with engineer NPC for a time). And the nature of NPC's wouldn't act any differently than it currently does, there's a timeline & my Hoary is different from your Hoary if I'm further along in the story. To make things easier & work with the story, it could be the Crystal Braves' Castle.

I'll actually look at this "Suikoden" game now, as I've never played it before.

Play them in order but skip IV or any spin-offs in my opinion!

So I'd say, play Suikoden I>II>III>V & stop.

Suikoden I & II are even far more nostalgic for me than virtually any of the FF's!

I/II are on par with any of the best FF titles & have unique gameplay elements from them too.

The soundtracks are AMAZING to get you amped up for it... https://www.youtube.com/watch?v=fPDs7ifXHGk

[QiLymePye]

Im a HUGE Suikoden fan and i must say that I loved 2 the best, but don't sleep on 5. Suikoden 5's story was amazing. Not as good as 2, but its up there. I would love a continuation of it as well as Xenogears/Xenosaga. But thats another thread. Oh and lets not forget Romancing Saga and the Saga Frontier Games....OMG.....im having flashbacks

[SendohJin]

To make things easier & work with the story, it could be the Crystal Braves' Castle.

but basically this is what they did with the Waking Sands and Rising Stones, it just seems like their characterization of an adventurer aren't the types of people who would own castles.

presumably, in Heavensward the story would have a new base of this type in Ishgard.

and parts of it would directly conflict with what has already been implemented for FC/Personal Housing.

[PlumpyMcduff]

but basically this is what they did with the Waking Sands and Rising Stones, it just seems like their characterization of an adventurer aren't the types of people who would own castles...

...and parts of it would directly conflict with what has already been implemented for FC/Personal Housing.

Not necessarily, it could have entirely different features.

Also, sure elements of this exist in the Waking Sands & the Rising Stones... true, but it's like you've mentioned, "in Heavensward the story would have a new base of this type in Ishgard."

So why not a Castle or Keep with additional functionality?

You mentioned that "their characterization of an adventurer aren't the types of people who would own castles..."

Yeah, maybe when the stakes were lower. But we're going into war, this isn't some underground operation anymore or mustn't need be.

Also, our renown is growing into other regions & across the lands--we're going to need better defenses & greater protections.

We practically merit a small army at this point & small armies need arms, equipment, food, shelter, & so forth.

Besides, I don't think it'd be a bad thing if this became the new FC Housing so Personal Housing could have the old FC lots since there's such an epidemic over the lack of space.