In practical terms, these are mutually exclusive. Maybe if raid content was the *only* content they worked on, or if they had a team large enough and diverse enough that they could afford to have an entire "raid team" that did raids and *only* raids (designers, programmers, artists, sound techs, testers, etc - *all* of them devoted to *only* doing raid content.) But on a project where that doesn't exist? You cannot possibly afford to devote that much effort and time to achieving both goals.
Personally, if I was in charge, I'd be working on making savage and ultimate completely, totally separate from normal and ex. They would operate on their own PvP-like toolkits and rules and stats. Every class has unchangeable stats, every action does a precise amount of damage or healing with a specific GCD (factoring in buffs that may need to be maintained, etc), and so on. Then, "regular" PvE would focus on fulfilling class fantasy first and foremost, and parse balance afterwards... because normals don't even *have* DPS or mitigation checks for practical intents and purposes, and Ex's checks are very, very generous (as long as your group isn't constantly fucking up the mechanics, you can pass Ex easily with pretty subpar performance, even MINE.) I want the raging berserker Warrior, the Dark Knight that uses their health as a resource, a White Mage that obliterates undead, and so on. Definitely the kind of long-term change and adjustment that would take a long time to implement, absolutely an expansion-level process. And like they're doing with trusts, I think I'd start by only having *current* raids and ultimates obey the new paradigm and... well, if the old stuff becomes "impossible" for a patch or two under MINE/ultimate sync, so be it. It wouldn't be the first time they've done something like this. Probably aim for each patch to bring an old tier/ultimates up to parity with the new system.
A lot of work up front, to save a lot of work down the road.
But why bother with that kind of work, when a majority of your income is from Limsa and Gridania ERP-AFKers? Those people wouldn't give a fig about such changes.