Making the ratio RNG of the character status and gear into 1:1 is the same for a fail game!
Altough there is alot of good ideas in this thread, along with bad ones. It's just a matter of filtering them.
In this case I'm with the ideias of aditional slots for gear, but, the gear should be divided on 5 tiers:
1-10 : Tier I ( 1 slot )
10-20 : Tier II ( 2 slots )
20-30 : Tier III ( 3 slots )
30-40 : Tier IV ( 4 slots )
40-50 : Tier IV ( 5 slots )
Also the HQ versions of gear and weapons shouldn't have an aditional bonus slot!! Aditional bonus slots should be going to the Primals weapons and NM gear/weapons, but, their lvl is also linked to the Tier of slots, for example: a lvl 15 weapon/gear dropped from a NM, instead of having 2 slots it should have 3 slots.
The meld system of 5 materias in one slot should be abolish! Instead SE should just allow us to input the materia along with the catalysts, these can be stil be used for materia input and output in the slots. Since catalysts are used to input materia they should be used also to output the materia of the gear/weapon.
I like also the ideia of having the materia growth system, but the spiritbond for these should be more slower, and the tiers II, III, IV, V of the materia should be removed. Instead of converting materia into tiers: I, II, III, IV, V; the converting system should be only grant a "tier I" materia with a random status like we usually get from any materia convert, and the spiritbond with the materia should increase the tier allowing to give a better booster of its status than the previous status of the lower tier. And this is the downside of materia growth system (spiritbond) the spiribond for the next tier is equal to the amount of exp gained from 1-20 (tier II ),20-30 (tier III), 30-40 (tier IV), 40-50 (tier V). Because spiritbond gear/weapons is so easy and materia spiritbond should be a challenge!
For these changes to be put in game, they should be followed with a few quests from the Goblin outside "Uld'a", along with the craftermanship guilds.
Hope these can help with this thread!