It's no secret that RDM is known by our en-spells in melee combat. If you go back to FF1, RDM had a spell called Temper which was basically an en-spell version of berserk. Anyways, my idea for including en-spells in FFXIV is more of a support element with a twist.
RDM's will begin by using their unique job ability which I'll call "Meld" for now. By using Meld, you'll lower your sword and apply magicial properties to it before holding it up channeling the effect in an AoE aura. I've changed the idea behind en-spells too.
For example, Enblizzard will stil do ice based damage, but now it has more of an effect. Not only will en-blizzard cause ice damage, but a freeze effect that works like a paralyze proc. The mob is frozen for brief periods especially if the mob is weak to ice magic.
En-fire or En-flame could be used on machines and undead mobs. Heat disrupts machinery and cuts though undead with ease.
En-thunder would of course have a stun proc, destroy machines, and wreck havoc on water-based creatures.
En-light and en-dark would work best on mobs weak to those elements. En-light could work like a Banish-like effect on undead. En-dark would be a Dispel proc and damage mobs weak to dark base magics.
En-aero would work well on rock creatures due to the eroding effect. Also features a silence proc which is useful on mage mobs like Soulflayers.
Well this is what I got so far. The idea was in my head, I personally would love to see a front-line RDM that works using DNC-ish buffs in FFXIV.