I'd much rather the Red Mage be original in its own right. I'm talking about using their own type of magic, with their own spells. We already have the Thaumaturge and Conjurer as hybrid classes, and the White Mage and Black Mage as specialized classes. That, plus the Arcanist and the Summoner. If they're going to add the Red Mage, then it has to be original.
How about making RDM a spellsword master? For example, buffing a sword and giving it special effects... not for damage but for other things like debuffs, or percent chances that a successful critical hit can drain enemy HP and split 70 percent of the hit to nearby party members. Classify RDM as a Disciple of Magic because, other than medium armor and using a sword, almost all of the weaponskills are magic-based effect skills. No shields, just one-handed sword. Maybe a charm or something on the second hand.
I didn't play XI for long (watched friends play it all the time), but I know that this game is not XI. So why make the RDM a master of all trades, if it just plain doesn't work with class balance? Make a new spin on it. I know it's not true to canon, but if it unbalances classes, then there needs to be an alternative idea.