...but what about warrior and monk? [...] But which abilities could they use to unlock the classes and still be different to the abilities those jobs could unlock on their own is the question. Warrior is a mix of gladiator and marauder, which in my mind would be one of the hardest classes to implement because really what could you give them that marauder and gladiator don't already have?
I think some assume that "weapon specialization" and "title" are completely different things, but they are both substantially just labels for looks and skills of a character. Titles just allow to give more unique traits to classes.

So, when you say "What do we give WAR that GLD or MRD don't have?" you are saying "what fighting skills we give to a fighter that a sword fighter and an axe fighter don't have?"
It's redundant. I believe in this system certain titles are better scrapped, like WAR.
Make melee weapon specialists have more unique titles, such as PLD, DRK, DRG... and make more new titles if necessary. There's no reason to cling to FFXI jobs precisely.
In the case of "WAR" it is already diluted in the other classes.

Melee classes are similar in their gameplay to FFXI melee obs. You go and maul the enemy with your weapon of choice.
Mages however are much more different. If you make a "BLM" you won't be redundant with the two base classes, however if you make a WAR title, you will.

It was already generic in FFXI, it would be simply unnecessary in FFXIV. GLD and MRD are your WAR. PUG is your MNK.

That said, if you all really like WAR as title, a warrior is "Someone adept at warfare combat" which means a fighter skilled at fighting in group against other groups. Give it AoE melee buffs/debuffs like "Warcry" from FFXI, dual wield, enmity bonuses, crowd control skills that allow parties to fight multiple monsters (like long lasting AoE stun)... which i don't think is that difficult to do.

Also, remember the system OP proposed is good because it's simple. Grids and other madness should be kept for future expansions.