Combo consolidation.
Basically, instead of having combo's taking up 3 buttons. Make them into one button that shifts through as you combo, like the PvP deal.
In addition, create new skills for those combo finishers that fork off the same 1/2 skills (For example instead of PLD having Fast Blade > Riot Blade > EITHER Royal Authority or Goring Blade you instead make it so that you get something like FB > RB > GB and Stab > Slash > Royal Authority) - Effectively reducing the number of buttons needed via adding new skills.
That way, classes with 3 different finishers only need 3 buttons for them all. Instead of the current where it's 3 buttons for EACH combo (Or at best 4 buttons for 2 different finishers, so for example PLD uses 7 buttons for its 3 basic 123 combos)
The only class I can see an issue for, is MNK because of the way their "Combo's" work... Unless you sorted them by positional requirements? So for example Bootshine > True Strike > Demolish, Dragon Kick > Twin Snakes > Snap Punch. With all the actions progressing depending on what Form is active (P.S. I would love if Opo-Opo Form was the baseline state so you didn't have to Form Shift to start a fight with Dragon Kick's bonus...)
REMOVAL of 100% uptime debuffs such as Slashing, Piercing and Blunt (Though that last one won't be an issue until we get another job that mashes faces)
REMOVAL of Protect, at least in its current waste of time state where it provides literally nothing to gameplay (Green Mage plx)
Role Actions killed and redistributed as Class Actions where relevant. Give them some job specific flavours if you wish.
I cannot say. As it means mentioning the Job That Shall Not Be Named and thus summon the hate brigade to come and derail the thread >.>
Edit: I may as well put in some pipedreams that don't relate to me writing a thesis on each class *Cough*
GCD reduced to 2s down from 2.5s (It feels 100x better to play when having enough SkS for ~2s GCD) with less reliance on oGCD weaving >.>
Stats that mean something. So that there's reason to have multiple primary stats for example. Make them all have some benefit for each class with just main stats being extra good for the class instead of the ONLY stat that's good for the class.
More diversity in secondary stats. Make it so that Crit isn't the god stat that triple dips into damage increase (It increases your chance at critting. It increases the damage of your crits. It generates more LB because crits have a bonus for LB generation.). Allow for more options as well as some more interesting stats like Multistrike (Call it Chain or something), Reuse Reduction etc.
More interesting materia. Make it less like "Build a BiS item" and more like FFVII where you slot in skills and effects and what not.
Rework to Limit Breaks. Both their generation and usage. Make them individual and provide much less impact but can be used more frequently (For example, what if Tanks used LB's to absorb Tankbusters for example) so that not everything has to be scrutinized by "Well this generates LB gauge so is a large tDPS boost!!!!" that things like crappy AoE shields from WAR/PLD are >.>
At least 1 of the Tanks will be unplayable garbage during 5.0.
At least 1 of the Healers will be unplayable garbage during all of 5.x
BLM will get at least 1 new skill that they don't give a damn about because its not Fire IV.
A bunch of meaningless [Skill] +1 ranks that give like 10-20 potency increase and that's it.
Yes, I'm cynical.