What if we got the Sub-Job System in FFXIV?

[Ameela]

First, these are just examples. If you don't like the examples, then envision an example that you do like.

If AST gave you Lightspeed every single caster would take it as it's too good of a skill to pass up, it literally makes a majority of casts instant for 10 seconds and reduces MP costs by 50% with 0 downsides.
I have a hard time thinking of what SCH could even give considering how much that job is about the synergy between all its different skills. This is also the case for Red Mage apart from Embolden I guess, unless a sub job would literally mean letting you use all of a job's skills in conjunction with your current ones which is just... horrible for balance purposes...
Everything else is just stuff that was already in the old cross-class system anyway: Internal Release, Mantra, Blood for Blood...
I don't like any example I or anyone else can think of, as this is a silly subject in my opinion, every job should be tightly designed in a way that it can work well with its own kit, otherwise you're just making every job feel like the same thing. This is a problem games like FFVI and FFVII face: when everyone can have every skill, what seperates the characters from each other (or in this case, the jobs)
I think they should just remove all this cross-class and role skill nonsense and give every job a fully functional kit that fits their class identity and is fun to use.

It isn't so powerful considering the only job that could utilize it with Swiftcast here is BLM, which simply puts it on the same level as RDM and SMN.

No it doesn't, have you ever thought about why BLM doesn't have a raise when every other caster in the game does?
It's because raising someone is meant to be a huge MP dump, you're not supposed to do it often, now what core part of BLM's kit goes against this design choice I wonder...
Also, in this hypothetical scenario, BLM is the only class in the game that would benefit from having White Mage as a sub job, as there's no other rez-less jobs with an insta cast, and you'll be hard pressed to find even healers doing slow raises outside of 24-mans.

[Freyt]

I don't like any example I or anyone else can think of, as this is a silly subject in my opinion, every job should be tightly designed in a way that it can work well with its own kit, otherwise you're just making every job feel like the same thing.

You're under the mistaken assumption that sub-jobs have to provide abilities that already exist. I think you could think of some kind of scenario involving sub-jobs that you would appreciate, and if you can't, then I would suggest that you're not thinking hard enough.