I could write an essay on this topic, but ill try not to here (edit: it turned into an essay....sorry). I played FFXI for 4 years, ending in 2008/2009. In XIV, Ive played since the very first Beta. There is a wealth of things I miss from XI. Ill try to focus on the topic of the end game situation you bring up. Some of the best memories and fun times I remember from XI were in HNM's and Sky. I can remember Vrtra fights that lasted over 4 hours long, Tiamat fights that turned into a circus as a 2 hour engagement suddenly went haywire and everyone died. Competing LS's scrambling to rez everyone so they could win the next claim and try to down it. HNM fights often turned into giant social events and competing LS's showed up and watched the fight, waiting to see if the LS fighting would die and give up the claim. I can remember hundreds of people showing up. Sky was pure genius in many ways. You had your trigger farming days, and when you had lots of triggers I remember some days where you killed a full Saturday just farming sky NM's. The whole LS would show up, even if everyone didn't get in on every fight they were all there, ready to sub in at any moment. As the leader of the guild during most of this, I could tell stories for days about what made XI's end game so enjoyable. While dynamis had its fun times, I wasnt personally as big a fan of it as much as some were.
So could XI style content work in XIV? I dont know. I think they could definitely borrow a lot of it, but it would have to be done in a more time friendly manner.....It would have to be "casualized" if you know what I mean. The end game in XIV right now, to me, is very underwhelming. Its a couple of 8 man encounters, and thats it. The 24 man raids in XIV arent end game content to me really, as they are tuned for the masses, and are push overs. I keep hoping we will see some new kind of end game content type announced, something to break from this current mold. I would love to see some over world HNM type content. The over world content in XIV is a joke. I suspect hunts were supposed to be a form of NM / HNM overworld content, but its unfun zerg content. The hardest hunts evaporate in 1 minute in a zerg of special effects.
In a nut shell, I would love to see XIV try to recreate some of the magic of XI's end game, while keeping it clear of some of the tedium it came with. This is one area XIV has improved upon XI - XIV has a tremendous amount of "quality of life" improvements, and I am not one who thinks adding old school tedium produces better game play. However, for all its gains, it really captures very little of the magic that XI embodied. The atmosphere is drastically different between the two games. XIV feels much more like a "production line end game development" if that makes sense. Its the same formula over and over again with each patch. I felt that in XI they constantly evolved new kinds of content into end game. XIV is all about glamour and minions and other casual fluff content. End game content in XIV isnt even done with an FC most the time, its all statics now, and often times these statics include members from various fc's. Used to, LS's (LS's were what FC's are in XI) competed for prominence and prestige in the server. It feels like for many people now, FC's are just social groups.
Im afraid we will never see games like XI, and everquest again. The landscape shifted with World of Warcraft. Players today dont like depending on a group to advance, and RNG has become the devil. This has led us to content that is focused more on instant gratification and predictable or guaranteed outcomes. This is why nearly everything in XIV is acquired by some type of currency. When everything is done via currency, then comes the weekly limits and caps. With the weekly caps comes the chore list. You can literally map out when you will acquire everything. End game becomes an empty grind to a predictable outcome. I've never jumped up in excitement at acquiring something in XIV, but I can vividly remember jumping and yelling when I finally won that prized item in XI. This is the trade off. I think the mindset of today makes it very hard to bring XI style content to XIV. Development studios are following the players, and players today are very casual. There is a reason why XI retained its playerbase for so many years. I played XI for 4 years without ever really "taking a break". I take breaks from XIV every few months though. Everything is just a chore in XIV - lots of "to do" lists but very few of the emotional highs that seemed to be readily available in XI. If you could put XI in the XIV graphics engine, and iron out a few of the quality of life issues, XI would be a superior game.