I've been back into FFXIV for over 2 years now and I find it much better than when I first played back in 2013. The first character I tried, which is listed as my main, was a Summoner and I loved it. I am a bit upset at the pet changes, loved sending Topaz Carbuncle/Titan in to tank while I cast from a distance, but I'll give it a try when I go back to pick up with ShB on him. While playing I tried to play SCH for a bit to see if I could heal. While the first time was bad, actually got booted from the dungeon while trying to learn, I also bought and tried WHM. I eventually came to the realization after going through a few dungeons with friends and coworkers from outside the game, that I'm not very good at healing. I had also tried tanking a bit by buying PAL, the same as my first character Aragorn that I never finished before then, and was ok. I'm nervous about it but still want to play the character anyway. The reason I never finished the first Aragorn was leveling was much harder in 2013. I eventually just bought the ARR story finisher and level 60 PAL for him and that's where he'll sit.
That's a bit of a long intro to set up my suggestion, but I wanted to give a thorough background. I like that fact that the Arcanist class has two Jobs for it, the DPS Job Summoner and Healer Job Scholar. I think it would be nice if each of the eight other classes each had two jobs as well, one DPS and the other a Tank or Healer, but not all 3. That's what the extra jobs are for. As I'm nervous and worried I may be horrible at Tanking I thought it would be nice to have another Job to fall back on without having to worry about getting another class/job up to that same level or push through until I can get to level 50 and get Samurai. It might also entice people to try tanking or healing same as Arcanist. Everyone of the friends and coworkers that play that I've talked about this with like that idea.
I have a few examples and I will refrain from names so as to not make it harder on the developers from using those names. With four tank and three healer jobs already, I feel the five DPS classes that would be getting tanks or Healers should be two more tanks and three more healers to keep an even balance. The first is Lancer getting a tanking job since it already shares with the tanks anyway. It could also share Paladin's shields if that give a hint of the name I've thought of. The other two examples are Conjurer and Thaumaturge. I would suggest that it would help to have these two basically swap White Mage and Black Mage, except for their elemental triples. Conjurer with Earth, Wind, and Water to Thaumaturge's Fire, Ice, and Lightning. Also like SMN and RDM, Conjurer's DPS would be able to help heal, even if it's just themselves. This allows the Healer a little more time to help heal the tank in difficult battles. They could also help raise fallen allies in particularly hard dungeons as well.