Here are a list of things I noticed that are not in the game that doesn't make too much sense at all- some of which really would not take much to add. I broken them down to sections on what they would relate to.
Instance Relating
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Level 60 versions of pvp modes. There is honestly no reason to not have a level 60 secure and slaughter front lines, it would certainly add variety to the roulette.
Ramuh 'glowing' type versions (Currently the only 2.x primal without an enhanced version)
Weapons for a harder Odin fight... I mean, he already got a sword skin from turn in, why not at least do his spear- Gungnir- if not other weapons?
And while on the topic of Primals... Revamp primal type fights. And also, properly name fights to "Normal, Hard, Extreme" where 'Normal' is typically story line relating, maybe even add "Savage" or "Ultimate" into this mix. Lets face it, most 'Hard modes' are mind numbingly easy so I never understood why they were ever called hard when there is no baseline for it being normal. Maybe even a new level of Savage/Ultimate where it would follow the current iLVL maxes like how Odin currently does and keep it as a challenge for people that want the primal challenge. Seriously, an Instanced Odin that is level 60 that requires i240 that can be queued anytime would be great, and things like this would give us reason to strive for the best gear.
Mechanical Related
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Class Specific Buffs on Gear/Materia. Seriously, something like "+3% damage on jumps" for DRG on certain foot gear, or even a "1%" materia variant that would be main slot only (think attribute materia) would make it so you have to actually think about melding a bit more. Probably even have it where you can smash certain V materia together to make these happen? I mean, the possibilities are endless- chance for instant cast, negating damage, enhanced skill damage... Hell, can even base it on current traits in the game or create completely new ones. LOTS of options out there and it would help us strive for our own unique setup!
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And while on the topic of adding uniqueness to our characters... How about a revamped skill system? You can leave us to picking the normal 5 'extra' skills but... Should we really be limited to 10 choices max overall especially with new jobs?
I mean, lets look at say, Warrior for starters- no matter what I do, my only options are savage blade (Why would I even want this when I have Skull Sunder which does the same thing but actually chains???), flash, convalescence, provoke, awareness, featherfoot, second wind, haymaker (Which would really benefit from the shield swipe treatment to be fair), internal release, and mantra.
The thing is, ALL classes have their 'savage blade', and then you got jobs like White Mage which has it even worse- They go blizzard II which ok, it at least binds stuff around them... But then they got Ruin which is a pointless skill when they already have Stone that deals more damage on earth damage (Not many things, if anything, takes advantage of element types, but that is for another day), but they ALSO get Physick which... does the same thing as Cure without the additional effect. That leaves them with only 5 skill choices, 1 of which is the previously Blizzard II. That is nothing for variety. That's a "You will have Swift Cast, Eye for an Eye, Virus, Surecast, and Blizzard II and like it" since Ruin and Physick are entirely useless.
Why not work job skill cross class in a slightly more strict version of class? I mean, if I go back to my warrior example and drop it down to Marauder, suddenly I have 31 skills I can slot rather then my shaky 10 and my white mage to conjurer gets roughly 24 skills (Still lots of useless ones like provoke, flash, bloodbath, but suddenly I get mantra which alone, on white mage would be HUGE).
This entire system needs a revamp.
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Quality of Life
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Server tags in Duty Finder- always nice to know if someones from your server.
Mechanism to Party/FC cross server and maybe new non-server tied housing zones for FCs only (maybe treat like instances?) I hate to mention other games but... Think GW2.
Linkshell & FC Recruitment that works in similar ways to Novice Network
*added*
Misc
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Ixali dailies- why not give them Crafter and Gatherer materia? Even if it's just IIIs, that would give some sort of incentive to do them again.