I'd like to start off by saying this is not another debate thread about what roles certain jobs should be assigned. Instead, I would like to throw an idea out there for jobs that could possibly fit into many roles. I'll be using Red Mage primarily as an example, but other jobs like Blue Mage, Dancer, and others, could take advantage of this proposed system.
The idea is not even new. The system is in the game, but currently serving another purpose. Anyone who has opened up their Companion menu would know what I'm talking about. While it is simplified for the AI of your Chocobo, you can set what kind of role you would like your companion to have; Defender, Healer, and/or Attacker. Why can't this type of system be used for a job that can fit into those three roles?
For instance, we start with a basic Red Mage. They usually have a rapier class sword, so we'll use that. They usually have black and white magic, so we'll stick with that. So from the very start, RDM could have the ability to do all three jobs. Parry tank (think Fencer), caster/melee attacker, and healer.
From that basic model, we could then build upon RDM. Picking which path we would like to take, and mapping abilities accordingly. If one wants to be a caster/melee attacker, they would use a system (like the Companion menu) to first assign the attacker role (this is for Duty Finder purposes). Once they have been established as an attacker, they would get access to higher tier black mage spells, as well as attack-based melee skills.
If they chose healer, they would be locked into that role, and gain access to healing abilities and spells. Tank would be mainly sword skills, and damage mitigation abilities/spells. Equip gear accordingly.
Meanwhile, the core of the job would not change. You would still have access to basic black and white magic, and basic sword skills, even after picking a role. Only by picking a role will you be granted access to higher and better skills for that particular role. You cannot be all three roles at once, but can change between roles at any time (except where prohibited).
This type of system could be used for all jobs that traditionally have access to a larger array of skills and spells. Plus it would prevent those types of jobs being forced into one of the three roles. Let me know what you think of this idea!