Someone made a post just like that with how gear could have certain traits, and then spiritbonded to be later unlocked so you can add them to other pieces of gear as you leveled up. So for example, at level at level 15, set of gear could have "Rampart: Parry +4", you spirit bond through that and it becomes unlockable. You can add it to some gear that gives you a slot. You could eventually make them so you're actually adjusting your abilities to whatever content you're using. Only thing I'd do is make some of the raiding armor have more unique things, as content grows old, some lesser skilled players can get it.
I'm not an end-game raider, but I do believe if you do things like Relic Grind or taking on the current hardest content, you should be rewarded with something extra. It wouldn't put you so far above the rest, but just enough to make you happy you did the content. It might even encourage others to start getting themselves to that level.
This might lead to something like "Players would neglect other players for not having certain boosts", this is happening now except with clears or having a certain iLV.
