I am not a big fan of the Armoury System. I think it is a convoluted mess that strips away the "Role" in Role-Playing-Game. All SE really did with this system is to allow people to play as a WAR/WHM, MNK/RDM, DRG/BLM or any other abomination of traditional (read effective) Party-Based Play without being ostracized, humiliated and bullied into changing their subjob.

Since our skill sets are private, we can play as any lame setup we desire and since battles are so chaotic and over so quickly, no one notices how badly someone is leaching and not really contributing. Now, I am no Elitist and I really don't care what or how anyone plays as this game is VERY solo-friendly so experiment all you want and create a Frankenstien Monster Hybrid if you wish but there will always be peer pressure (elitism) when it comes to Party-Based Content and it is specifically for Party-Based-Content that the new "Jobs" are being created for.

No Party will want a Lancer/Paladin (unless no Glads are available).
No Party will want a Pugilist/Paladin (unless no Glads are available).
No Party will want a Conjurer/Dragoon. (period)

Yes, elitism sux but that's just the way it is and always will be cuz PT's always want the most efficient party setups, whether it be for EXP, NM's or Raids. Do and be whatever you want for solo-play but everyone eventually has to conform to the standards of what is "best" for PTing.

I could be wrong (I often am) and I am just speculating (along with everyone else) but I think the new "Jobs" are specifically designed to enhance Dungeon/Raid fights where specific monsters are fought and specific goals are met. In other words a "Paladin" would be very beneficial against a Dungeon Boss (perhaps required) but useless against random mobs in the open world (no real benefit so not even available).

A "Thief" specialty would be very useful for getting that rare drop in a dungeon (Treasure Hunter) but useless in open world (TH does not affect "normal drops").

Maybe they will make the "Jobs" available to any Class at any time but it seems rather pointless to me and would just make an already muddled game even worse.

Sandboxes are for children. Games are for teens. Jobs are for adults.