Variance in player skill is hurting FFXIV's itemization design.

[Kaurie]

I don't think that's what he said. I think what he meant was "why should interesting bonuses be limited to raid gear". As in, if they decide to add some sort of bonuses outside of stats and sub stats, like "cure 1 potency +50" or whatever, that kind of system should be available on both raid gear and non-raid gear. Sure, have the types of bonuses be more effective on raid gear if you want, but the system of it shouldn't be locked to raid gear.

Personally, I think it should just be done through materia - where the set bonus stuff is in raiding. However, if you don't raid, you can just buy the materia off the market board. Similar to how people need to buy crafting stuff off the market board if they don't choose to partake in crafting (i.e. foods, potions, crafting materials for relic etc.). Makes it accessible for all, provides incentive for raiding, gives interesting bonuses for raiding and to gear etc.

They could also do set bonuses that are achievable through other means, but perhaps are less nice.

i.e. Alexander Materia V
Provides +5 crit, +5 sps, +5sks, +5 det
Secondary effect: when two different pieces of gear have Alexander Materia V slotted in them, the wearer gains the following bonus - SMN: reduces MP cost of Ruin III by 100, BLM: increases timer on Enochian by 5s per refresh, WHM: Cure II procs are now instant cast, etc.
(I was going to make more, but it's hard to make these up on the spot in a semi-balanced fashion, naturally testing would be vital to implementation).
Tertiary effect: when four different pieces of gear have Alexander Materia V slotted in them, the wearer gains the following bonus - (more bonuses, perhaps this would could just be something like +Main Stat etc.)