Limited jobs are unnecessarily isolated from the rest of the game. They can easily be linked to normal combat jobs, and this would make both limited jobs AND new DPS jobs more interesting.
The next Magical Ranged DPS job should be "Unlimited" Blue Mage: a fully fleshed-out combat job like the other casters, but with spell names and animations lifted from the BLU spell book. In order to unlock Unlimited BLU, you have to learn its full roster of spells and abilities via the limited job. This unlock can be split up into level brackets, with Unlimited BLU being unlocked first up to lvl 60, then lvl 70, etc., as you learn more spells.
This makes the limited job more interesting, because it gives us a big reward for playing it that's connected to the rest of the game. It makes the next DPS job more interesting, because for once, we have to EARN it (usually, we just talk to a random stranger in Limsa Lominsa and instantly receive expert knowledge of an ancient combat art). I can tell you that this would increase my interest in Blue Mage 100-fold, and it would get a lot of my friends to try out BLU too.
This system provides a natural choice for both the next ranged physical DPS, and the next limited job: Beastmaster. One vision of how it could work: Wielding a crossbow, the limited job focuses on taming and training a huge variety of beasts, while the unlimited job focuses on 3-4 beast archetypes with different support sets, similar to old SMN egis. Every beast in your limited job menagerie falls into one of those archetypes, and the unlimited job can pick any fitting beast they want to serve for each archetype (basically, egi glamours, but personalized to your favorite beast companions). The unlimited job is unlocked when you have a fully trained beast of each archetype. Like unlimited BLU, there can be a stepped unlock for progressively higher levels as you fill out the limited job.
Yes, this would require a lot of work... but probably less work than creating an entirely new job from scratch (or two fully separate jobs, in the case of Beastmaster). It would make limited jobs interesting to a wider group of players, and would be an innovative way to make the addition of new combat jobs more interesting. I humbly ask the dev team to consider this idea, and other players to provide feedback.