I'm one of the players that got hyped to play FFXIV because of a Job that is only unlocked at high level. It's incredible frustrating to play the entire ARR, and man, it's not a fast travel, just to play your desired Job.
I'm here because I know a lot of friends that share the same frustration, and I want to suggest improvement for starting Jobs. The fact that they didn't showed any of the changes to the battle system makes me worry, and encourages me to call for this suggestion.
Similar to the Minstrel's Ballad (Ex versions of Trials), there could be in the starting cities a new NPC that can reward you with Special Job Crystals, so that you can charge it up, and give it back to him. These crystals will only let you level up until the level of the starting quest of the Job, then you need to return this "Charged" Job Crystal to the NPC. This NPC will also reward you with a special weapon that functions similar to the Aetheryte Earring, auto syncing the stats based on the player level, until the level of the first weapon available. Obviously, the player need to buy the proper expansion to have access to the Job.
For example, if the players choose Red Mage to be the first Job in the character creation he will receive the special weapon, which will auto sync up to lvl 50 where the first weapon is available, and the special Job Crystal, unlocking the level up to 50. To progress you need to complete the RDM unlock quest, and retrieve the Special Job Crystal to the NPC.
Now, for Dark Knight, Machinist and Astrologian, they will need to change the quests to not give Job Actions up to level 50, where we can access Ishgard. So that these jobs can auto learn actions by leveling and start learning through quests at 50+. Or remake the quests up to Lv 50.
Or, Ultimately, simply by letting the player choose the first Job from character creation, implying that the player had that Job before arriving into Eorzea.
Edit: Maybe the answer to this is to create Classes to expansion Jobs that start in the starting cities, with minor lore. Then, let's say AST, by reaching Ishgard with the class, then he can learn the Job.
I say game-play first. FFXIV is turning into a really big game and SE really needs to address new players experience. Looking at you ARR MSQ too. I think that it's not good to keep improving and letting old OBLIGATORY content not showing today's quality. Is it the right decision to just say to the new players to pay to skip old content? Old content is worth experiencing in my opinion. It was not easy to play with a Job that I didn't like just to play Dark Knight. I felt rushed, the MSQ felt too long, I've skipped some of it just because of this system, just to play Dark Knight. I don't want anybody to feel encouraged to rush through the MSQ just to be happy.
TL;DR Let the players be happy since start, don't place the MSQ as a villain to those who only want to experience the MSQ first time with the Job they want. The reason they are locked behind high levels is not enough for me.