It wouldn't because while 'anyone can res', it'd be limited, RDM and healers would be still able to cast their res as many times as they like (presumably). I would suggest making the 'phoenix feather' charges be shared across the party, so if someone uses it, it depletes a charge from everyone, that makes it the final 'absolute emergency' button
1: I want SE to do the obvious, and merge Grade 1-5 into a new 'Grade 1', and then subtract 4 from each current grade of materia. 6 becomes 2, 7 to 3, 8 to 4, 9 becomes the new 5, 10 the new 6. This doesn't fix the issue per se, because SE is going to add another two grades and repeat the issue again next expansion most likely. I've suggested a 'High Materia' that can only be melded to the weapon, and you can only have one, which provides a Job specific buff to something (ideally not damage unless you're a DPS for balance reasons). Stuff like a choice between 'Kardia is now AOE but slightly weaker' versus 'You can activate Pepsis right after a shield breaks to get partial healing still', or 'Dark Mind now has 10% physical mitigation too' versus 'Living Dead CD reduced by 1 minute so you can do WAR exclusive cheese strats as DRK too'. Instead we'll get grade 11 and grade 12 materia, which will give +15 and +60 stats respectively
Also, by merging lower levels of materia, the ARR relic becomes a lot easier, as you'd use the new Grade 1 for the full 75 materia. Grade 5 (which would become Grade 1 with the merge) is a potential reward via Mhachi Matter, which can be obtained via Wondrous Tails and other sources, so we don't need to rely on weird methods to earn the weird grades, like afaik the best way to get grade 3 is via submarines, and grade 2 is 'spiritbond or bust' probably
2/3: I wish they'd just merge Scouting into Aiming, and Maiming into Striking. They should have done it a long time ago, if they're going to keep refusing to add another DEX melee. Heck, SAM could have been that DEX melee. Or RPR could. But yeh, just make DRG/MNK/SAM/RPR share gear (SAMs now able to get more armored looks), merge NIN with the Aiming set (so NIN mains can actually flex to a different job with their earned gear). Also fix the glamour system properly instead of constantly band-aiding it with 'we gave you more space'
4: Just copy other-game: you start with 1 charge. After X minutes of combat, you earn another charge. Healers and RDM/SMN keep their 'utility' as their res is not affected by the charge system, they can use as many as they like. The only real issue I foresee with a system like this is that in a situation like A4S, the healers would be first to be sacrificed to 'cheese' a mechanic, as the issue of 'well if we sac them we cant res' is gone, and they're the lowest damage. On the flipside, I guess that's technically possible now as SMN and RDM would just use their current res options to res the healers.
For balance, maybe the Phoenix Feather res always resses people straight into Brink of Death (the 50% penalty)? You would want to have a proper res if possible, but if worst comes to worst, you burn this instead.