more a presentation of the "idea" than anything solid.
1) MP/action economy
Battle starts with 10 MP, except for certain class bonus (below) and some equipment.
ELEMENT1 spells cost 0 MP, stronger and more specific spells > 0.
Magic damage is reworked so that even the lowest spells remain relevant by changing fixed spell power into a percentage modifer of the weapon power.
Staff and Rod provide and small bonus on top of that.
Guarding grants 100 MP, next to the usual recovery options like Ethers and Osmose.
If MP is at least 100 at the end of a turn, that character skips wait and immediatly gets to act again.
ATB only moves when noone can do anything.
If you're seeing parallels to Bravely Default, it was kinda the inspiration.
And yes, that makes the Quick spell useless. Will be replaced.
Hmmm... one source of bugs less, strike!
2) classes
We have 4 characters and all have access to the same 22 classes, including Freelancer and Mime.
No more!
Noone gets to keep the Hobo class, they learned a profession after all :P
Aside from that, I block 6 classes per character, so each one has 15 classes to choose from. E.g. Bartz can never be a Chemist while Lenna just doesn't have it in her to go Berserker.
Less breakage, more character diversity.
Each class gets to teach 7 abilities, some duplicates across classes for the basics, but the heavy stuff like !X-Fight and !X-Magic should stay unique and as a 7th ability.
Additionally stupid stuff like White1-6 goes and only teaches White once. You don't have to learn 6 times how to wield a sword either, neither has !Blue that problem.
Changing into a class no longer changes stats, instead levelling a class grants permanent stat bonuses, 3 out of HP, MP (starting bonus and max), STR, AGL, MAG, VIT. Duplicates possible.
E.g. each level of Monk gives +2x VIT and +1x HP (30 HP before VIT %bonus)
ABP required is not based on which ability you learn next but purely on how many class levels you already have.
From the 30th class level it costs 999 ABP then. I've so far decided against a hard cap of class levels.
3) items
Consumables aren't used up, instead you get a cooldown during which you can't use !Item.
Higher item stacks increase effect or lower cooldown. E.g. 1x Potion heals 30 HP, 99x Potion 2000 HP.
Mix still uses items up because it is that broken.
Undecided on Drink and Throw.
Out of battle healing is not possible anymore (except for tents), instead you get a free partial heal based on VIT on victory.
4) equipment
Equipment is changed from Helm, Armor and Relic to 3x Relic.
Non-shields have to get renamed.
5) elements
Everything should get one of the eight elements this game has instead of 90% neutral.
Weapons belong to one element per type, i.e. swords would be fire except for special cases.
Armors for defensive obviously, each element would give 2 resistances and 2 weaknesses, mix gear badly and you're suddenly weak to 6 elements.
The only thing I'd allow to be neutral would be the final boss. Everything else, enemy or otherwise, should have elemental affinity (i.e. weaknesses).
Also, I'm still stuck on the biggest hurdle: the hack's name.

I've decided on the acronym, not on the long title. Go figure...