A constant issue in this game is the concern that our gear is so quickly "obsoleted" by newer content and rising iLevels. Many have expressed a desire for more horizontal paths of character progression, though this is understandably difficult in a game built to be very much vertical.
One of the big obstacles is the lack of mid-battle gear swapping. I'm personally thankful that's not a part of this game. However, gear swapping in FFXI was a big reason why the horizontal progression was so successful -- players could literally spend years chasing different pieces of gear for each spell and ability.
Here's a way to bring that element of gameplay into FFXIV (to a lesser degree) without reverting to mid-battle gear swaps:
Introduce exotic armor pieces.
In the game Destiny, you can only equip one exotic gear piece at a time. I think this is how it should work in FFXIV, too -- or perhaps two at a time (one left side, one right side). And each job could have exotic armor pieces available for each slot.
The exotic armor piece could be either +5 or +10 above the current iLevel cap. It would have amazing stats. Each piece could also offer a unique bonus that would be great in specific situations (+20 det in Diadem, +10 physical resistance vs. Primals, etc.)
Even though players could only equip one or two pieces at a time (which would keep them from breaking the game), the concept is that players would still pursue them because a) each piece would be helpful in different types of endgame content, and b) with better stats/iLevels, these pieces could essentially have double the lifespan of a normal piece of upgraded tome gear.
And to please the hardcore raiders (and I'm totally not a hardcore raider), exotics could have a fairly high drop rate from the final bosses of the most currently difficult raid boss. These would also be available in other ways, though, such as through NMs spawned by pop items farmed in Diadem. Lots of options here.
If we wanted to borrow a page from FFXI, then these exotic pieces could also be upgradable in future patches through "Trial of the Magians"-style content. It could be a grind-heavy path that would essentially allow anyone the chance to keep at least one exotic piece up-to-date in the same way that relic weapons are enhanced between patches.
Anyway, that's my idea. Seems like exotic gear could bring some much needed persistent gear into the game without making existing options for obtaining gear any less desirable.
Plus, the methods for getting that gear could be a lot of fun.