If you could adopt and adapt a system from any FF title...

[Skies]

Definitly in with Majidah there, FFVII's Materia system.
Although, that would be a thing that would require the entire game to be built around it, so it certainly could never make it into this game but even so, another MMO with that sort of ability system, I loved that.

[Fear]

XII is the most feasible, seeing as how it is basically XI, but you can control your party o.o

If you want that may as well give everyone a bot, because thats all the Gambets did is controll the char for you.

[Asiaine]

FFVII Materia System.
By far and away the BEST battle mechanic I have EVER seen anywhere. The beauty of customisation, the individuality of strategy, the satisfaction of materia growth, and the certainty of outcome.

It was as perfect a system I have ever seen and I dare say if nothing else was given to me for 2.0 but a change to FFVII materia system I would be a happy bunny indeed.

[Felis]

Chocobo breeding from FF VII
Bring 2 chocobos together to get an egg ^^

[Zetsumei_Tsunarashi]

If you want that may as well give everyone a bot, because thats all the Gambets did is controll the char for you.

Yep.

The Gambit system also allows for auto-leveling tactics where the player can leave the party leveling and gaining EXP without having to as much as touch the controller.

Negalmuur in Stilshrine of Miriam is a famous auto-level spot: it will frequently summon Ghasts and by correctly setting up the party's gambits it is possible to create an infinite loop, which allows the game to be left playing while the party continues to gain experience.

[Elexia]

Yet VII's materia system was utterly broken due to some of the parameters not actually working and made everyone the same damn character because everyone could summon/cure/etc so it's not good for an MMO envrionment, hence why they got rid of absolute freedom :\ I'd adapt the Nyzul and Einherjar system. Random dungeon layout + puzzles + fighting till you gain access to Odin while gaining currency to buy shit you actually want?

Sign me up for a good system.

[Saifaa]

FF Tactics job system as far as i'm concerned, combined with something else to acquire abilities. Something like the guild marks (getting them like before, unlocking depending on job/class rk and corresponding quest done, was a fine system imho) (blue will get something like IX/XI, but needs a one-use "capture" ability that can be bought with gms ) + Physical level (allow a nice level of originality/specialisation of your char).

Call me nuts for loving those old systems, but they were the main selling point in my case.

Materia as it is now, with special combinations

[AdvancedWind]

Final Fantasy XI Blue Magic.
Final Fantasy Tactics support / reaction abilities, unlockable in one job and available to all.

[Sav]

First though, might wanna give mobs some spells that are diverse and unique. Would make learning magic much more interesting and fun ^^

This is my concern with blue mage. I haven't really seen any monster abilities that make me think, "I WANT THAT!"

[Elexia]

This is my concern with blue mage. I haven't really seen any monster abilities that make me think, "I WANT THAT!"

Yeah, XI was truly built for Blue Mage, XIV is not honestly, especially since everything is an ability even spells.