I can see RDM as a the second GLD job. Yes, a fencing style sword is the weapon they're depicted with, they are usually proficient with many 1 handed weapons and shield use. So just make their relic weapon a fencing foil and there you go. For XIV ARR's iteration, they should be primarily a close range dps, their combo attack starting with melee, then ends with a magical attack. They would also get one that'd end in a cure of some sort. Just enough to give some breathing room for SCH's and WHMs. Might be either a weakish cure, or one that only can be fired every so often.
On the other side, the DPS version of MRD should be Dark Knight, who can either use their own HP to cause big damage, or drain HP with their attacks. Again, just make their relic weapon appropriate, they're proficient in many 2h weapons. An alternative is to have them be Berserkers, but I think most people want to see Dark Knights.
CNJs would have geomancers as their dps, but would have to be ranged DPS since staves and wands suck for dps. I'd actually have them not do much damage by themselves, but have their attacks make other attacks more effective. It'd be a neat way to reintroduce elemental attacks back in a bit.
I'd like to see THMs become Oracles, who actually get debuffs that are strong enough to effect even bosses as opposed to doing damage output, but that'd put them outside the Holy Trinity of MMO roles, and thus probably not something SE is going to want to do.
Again in the "wishful thinking" catagory, I'd like to see PUGs become some sort of "off-tank" class. They would get some sort of short term agro management, something that would automatically make an enemy focus on them for set period, maybe an ability that would make a enemy automatically target their next special attack on them instead whoever has agro, that sort of thing. Would probably have to be a new "Job" entirely, like Grappler or something.
A tanking version of lancers could be Samurais. I -know- that Samurais in FF games typically use katatnas, but in the games they're usually proficient in spears, as well. I know it's a bit of a stretch, but there aren't many other established jobs that use spears.
Honestly, I'd just overhaul Archers, introduce rangers, make them a pure ranged dps class, then make BRDs the buffers they used to be. Either that, or given them Snipers like Mustadio from FF Tactics and be the alternates to BRD's, primarily dps with some debuff ability as opposed to buffing. That might be a bit of a ripoff for ARCs though.