I've tried to say, that additional DPS complexity would theoretically be balanced such that it is mostly ignorable in all content (eg on SCH you wouldn't need to do stancedancing to get the +20p via Offensive, even in an Ultimate). This mentality of 'you need to do the optimal damage or you've failed at the game' needs to stop, so we can get back to 'the most important aspect of clearing the fight, is clearing the fight, not the funny coloured number you get afterwards'. We're playing FFXIV, not FFLogs
But ignoring that for a moment, I would look at the other parts of the kit, and I'd argue (though I might be biased) that some of the changes I listed would make even an Ultimate easier, rather than harder. Take TOP for example. P6 can be a struggle for SCH because it has to stand still to cast its barriers. With the rework I laid out on page 1, a SCH could ignore Strategy: Offensive (because they don't need the bonus potency to clear because PCT now exists/potency 'bonus' is tuned to be 'optional optimization' in all content, even Ult), and instead camp in Strategy: Defensive for the whole of Phase 6. With that, comes a modification to Indom that makes it an instant OGCD Barrier effect every 30s, Excog gets a Galvanise attached that can be Deployed, Protraction can be Deployed, Fey Blessing gets turned into a Barrier (which then gives a regen when it breaks), etc. There would be so many more tools at the SCH's disposal to overcome that weakness of 'I can't really cast barriers very well while I'm running to dodge stuff/get to position'
WHM would have an additional healing action that doesn't cost damage, reducing how often the player has to rely on Medica spam/Cure3 spam, and would have around 60% of its damage actions be instantcaasts, vastly increasing its mobility (especially good for keeping damage up in phases like Hello World). SGE would have the ability to apply barriers without dropping its damage, via Kardia manipulation, and the reworked Krasis would allow it free movement with any action (giving 4 stacks of 'next spell casts instantly'). For both of these, avoiding needing to GCD heal means dealing more damage, and that makes the DPS check more lenient. However, for those SGEs who want to play 'safer' by relying on GCD shielding (eg they don't feel confident they can do the 'set up' required for Kardia-based barriers, and prefer the 'on demand' nature of E.Prognosis), they'd still be able to do that, as the DPS check of TOP was designed with that strategy being 'the only way to do it' back then.
The one that I might agree with, that 'it might be too complex for Ultimates', would be AST. But AST has always been busy to play, look at EW AST with all the Draws and Plays in the opener there. I don't think what I had for AST is necessarily 'more complex' to execute than something like EW AST, but it could be argued that this reworked AST has more 'burden of knowledge' due to needing to know card effects. That, however, could be addressed with UI elements, such as how cards got a coloured border on the job gauge in EW to denote if they're Melee or Ranged. So a card in this system, let's say Bole, would have a symbol next to it to indicate 'this is best on a Tank'. But as a reminder of how much 'simpler' EW AST was to execute in an Ultimate compared to what I posted here, here's an example of EW AST's opener (thank you Fanbyte):
I've not fully thought about it, but my assumption for this redesigned AST's opener would be...:
Earthly Star > Potion > Prepull Malefic > Royal Road > Play Major Arcana > Malefic > Royal Road > Divination > Malefic > Play Major Arcana > Oracle > Malefic (opener ends here, spam Malefic until Minor Arcana comes up)
...Maybe with a Redraw or two in there, depending on how the cards come up. But even including as many Redraws as possible (assuming the worst 'luck' with cards), this opener still has less APM than the EW opener. So the source of this AST's complexity can't be from its mechanical execution, but rather, from having to learn all the new card effects. But as mentioned above, A: Card effects would have 'assistance' in the UI, to help teach new players which card is best on which role, and B: while the job would ask that you learn 6 Major Arcana effects, 6 Minor Arcana effects, and then 3 Royal Road interactions, these are split up into brackets at level 30, 50 and 70. So a veteran player would have all these changes thrown at them at once, and have to learn everything in one go, but the player who picks up this AST fresh, would have 20 levels to get used to the Major Arcana and internalize how they work, before being presented with the next chunk of knowledge (Minor Arcana), allowing them to build their understanding of the Job's systems in more manageable pieces. That's the whole point of the levelling process, surely?
For a Veteran player, who is having trouble internalizing the changes (because they're trying to learn the level 30, 50 and 70 knowledges all at once), luckily we have a system in the game wherein we can go back to older dungeons, and be level sync'd down to a lower level. So, if this system were implemented in the game, personally I'd run a dungeon like Brayflox Longstop a couple of times, to learn the Major Arcana effects. Once I'd done that to the point where I'm 'comfortable', I'd move onto a level 50+ dungeon like Sohm Al (not Dusk Vigil cos I hate it) or The Aery, and practice in that level bracket a bit to get a handle on the Minor Arcana effects. At the same time, being in that level bracket would allow me to test myself and see how well I've learned the Major Arcana effects too. Finally, I'd move onto level 70+ dungeons like Holminster Switch to learn the Royal Road interactions. Throwing yourself into the deep end in a current dungeon, while not my personal recommendation, is also entirely possible now without feeling like you're griefing others, because we can do Trust dungeons too
I do agree that there needs to be some consideration applied to making sure that old Ultimates don't get 'harder because my job changed', because that's a worse feeling than 'old Ultimate (cough UCOB) doesn't have a DPS check now that SMN got reworked'. I just don't fully agree that these reworks would necessarily be enough to create that feeling of 'old Ult got harder'