I very much doubt SE will change the game mechanics to make one or two exceptions just to make one job work Gukie. Frankly I think the MP limitations from being engaged would be one of those things that could keep RDM from being OP, but unless it's magic / support abilities are somewhat tied into their physical offense we'll likely see a repeat of the backline Red Mage just because we'll have a slew of RDM's who can't manage MP effectively.
And before people say "That's what Refresh is for", I've been specifically avoiding the spell in my ideas because it specifically turned against RDM in FFXI. Despite what people think the developers originally intended for Refresh supplement Red Mage's ability to be in the front lines without stopping to heal every battle. Things didn't go as intended, people found the hidden effect of elemental staves, series of other unfortunate events, BAM RDM was cemented in backline position. Of course since only a few jobs actually utilize mp, it might not be so detrimental (especially if it's AoE) so it might not be so bad. But if then again it might enforce BLM stacking with Ballad / Refresh giving insane MP regeneration. So for now I'd much rather avoid "Refresh" outside a self-buff only, trait, or find ways to restore MP through other means like Runic Blade / Aspir.
Actually the original concept had little problems, it was the overall design of the game that made it difficult for RDM to actually play as it's original concept. SE improved on newer hybrid jobs like BLU and DNC by tieing their ability to function as a mage within their melee, however RDM was so pigeonholed into the backline position for so long and to make it comply within it's concept would require the job to be entirely rebuilt a 2nd time and perhaps rebuild the magic system altogether, SE just said it wasn't worth fixing at that point.