I hope they have the foresight to include some porter moogles in the prep area because while it is going to be interesting to have jobs rely on their vanilla kits, it certainly makes a diverse pool of equipment that much more important. Time to dust off the old crossbow/status bolts on Thief...
I can see jobs like Blue Mage being relatively "subjobless-proof". As already mentioned, other jobs, notably 2-handers, are going to lose a lot of offensive presence without a sub. However, they are also taking a fair chunk of some jobs' defensive capabilities away and that should be equally impactful in many cases.
I'd say I'm interested in seeing what kinds of new setups/builds are going to come out of this but the reality is probably that it's going to be metagamed and we'll have "Use ABC jobs for ___ NM so you can have XYZ left jobs for ___ NM" as the dominant strategy fairly quickly. Overall, I think treating jobs like a limited resource is a unique idea, and it's going to be fun for some groups to figure out things like which fights to use your 2 instances of Dia on.