It never really works in any multiplayer game. There is literately no way to make a game fair if the differences are too far apart that the meta becomes "use this exact build or you will be excluded from all content harder than facerolls." Which, guess what, was the case for most of 2.0 and 3.0 when the jobs were the most different. Right now it's like 'use WAR, or don't bother raiding as a tank'.
Like if you think about why the game does what it does, it comes down to fight choreography. If you have 3 different tanks and one is weak to piercing, one is weak to blunt, and one is weak to slashing, but you design the fight around each boss having this kind of combat, then you get painted into a corner where players will demand the content be nerfed.
Likewise with the elemental strength/weaknesses. It only works well when players can have that ahead of time. So as far as tanks and healers go, you can't design this. Since you can't have 6 DPS players, you can't have one player with each element, nor can you have each melee DPS with slash, stab and blunt.
I understand why they removed these elements, because it makes the PUG duty finding impossible. You'd have to make it so that duties have 1 of each which means you'd end up with 6 element casters (DPS, or healer if it calls for "Light",) 3 melee or ranged DPS, and with so many DPS you'd have to nerf everyones DPS down.
Unfortunately that means re-designing things in a way that would require changing everything. It's far too late in the game's life to do that. Never try to turn a game into something it was not. This is why FFXIV should never have had PvP, and should never have had the Deep Dungeon. The former because they had to effectively create a second game on top of the first one for it to work. And the latter had to be an alternate dungeon system. Sure the Deep Dungeon, is fun once or twice, but it's basically just "easy mode leveling" instead of playing the DF content.
So if you change things to be ability points, what are you going to do with the PvP? Pretend it doesn't exist like normal? What are you going to do with the Deep Dungeons?
It's just that I don't see what they want to do here. Unless they are going to basically add yet another dungeon mode, and basically go "Hey we're sending you back in time before the world was sundered, and also you have amnesia and don't remember any of your skills." Before the time of the ancients. I don't see how they can logically do this.
Maybe they could get away with having the player have to solve a solution to rejoinings, which involves going into each reflection and each reflection has a different combat system that has levels independent from the source.