Aside from the bluemage/geomancer stuff that might actually be coming in 5.0 i would love to share this idea/fantasy of additional roles to existing jobs with a seamless integration with current systems.
The premise is pretty simple: Introduce new weapons for existing jobs with a new role for them. If we're going to Garlemald in next expansion what better place to introduce a new weapon: The Gunblade.
This is a second weapon that Machinists can equip in place of their existing Muskets. The rolemodel for this is Gaius van Baelsar - a melee fighter with some ranged abilities that lets the Machinist be a Tank for Duty purposes. [Promo image link]
Another weapon that could be introduced is the Two-Handed Hammer for Paladins. It would let them fulfil the role of Melee Damage. [Promo image link]
The Orb would allow the Black Mage to become a tank. To differentiate the them from Astrologians the mage would hold the orb under their hands [like this]. [Promo image link] Alternatively this could be a secondary weapon to be equipped [like this].
The last example will be the incense burner for Monks. This would allow them to become healers. [Promo image link]
Other weapons:
Javelin for ranged Warriors.
Dark Knights have Darkside, just use that for melee damager. (I really want dps DRK)
Padjali Rings for caster White Mages.
A magical garlean Pen for caster Scholars.
A hand-held radio telescope for caster Astrologians so they learn to do some actual science for once.
A pet dragon for tanking Dragoons (you ride the dragon like a mount).
Bandages for a healing Ninja. Yes, you become Sakura from Naruto
An Odachi for tanking Samurai.
A garlean Microphone and speakers for singing and dancing healing Bards.
A Tomestone for sophisticated tanking Summoners. They become the primal avatars - ifrit for aoe tanking and titan for singletarget tanking.
A dagger+focus for healing redmages. Similar gameplay but reversed for healing.
These are examples to explore this idea, some of them are silly, yes, but i think it's cool to explore something like this that expands existing jobs.