So much would need to be redone.
First thing would be...
slash 1/10 gil again.
Make Materia chances rarer.
All gathering materials rarer.
Adjustments to all side & main quests rewards.
Adjust repair costs/housing costs/removal of npc items from shops
All materials get 1/10 slash.
Adjust all exp rewards for gathering & crafting levequests.
Lower Fate EXP reward
Make Fates Rarer Spawn
Lower Dungeon EXP reward
Lower Monster Exp reward
Change Crafting system where you cant HQ everything.
Dungeon item drop rate drop to 30% and lower.
Lower drop rate of all currect 100% items. Such as Primal Weapons, gear etc.
Make Crystal Tower drop all loot at the end of the dungeon.
Remove Phil & Myth rewards after content
Lower chances of gathering HQ items.
Remove player's class levels earned through patch 2.0 & 2.1 by 50%.
Increase enemy damage under lv50 by 25%~30%
Add tier5 Materia, lv90 craft gear, new materials
Adjust how what materia comes from what gear.
Make all currect equipment with Materia on it Blank Materia.
PVP gear has no materia melding risks.
1.0 items will be useful once again.
Adjust crafting recipes
Equipment adjustments
Option to resell equipment like in 1.0.
Pretty much all of that would be first step to fixing this game. Alot of players already got levels,gear,materia,gil,items and a reset is needed to repair alot of the damage already done.
Future adjustments
Allowing players to re-obtain blank melded equipment to its currect status with some risk.
One Class= One Job
Class/Job Adjustments
Give SCH its own class.
Reseting ARC point attoement
Allow more cross class actions on Jobs.
Adding new types of Materia with stats like double attack+ & TP+
Converting all treasure maps to Leather Maps and adding tier system where you find maps in other treasure map chests. Doing more higher tiers of maps increasing the rarer loot & harder enemies.