I sound like a broken record but a healer job that focuses specifically on using their GCD to support the party between heals instead of spamming dps could be a good concept for a unique ffxiv job. Something like Astrologian, but with support spells being cast during heal downtime instead of spamming dps filler.

Weapon could be something really out there, like the measures from FFXII, or a bag full of aether charged crystals (though the latter verges into Chemist territory)