I'm not against the idea see no point while ilv > crit > everything 99% of the time.

Gear swapping was an important part of FFXI.
But there you had gears that actually mattered and affected certain parts of your kit.
Ex: You could stack healing potency gear before using curing waltz on DNC.
Or why not use gear that reduce TP cost. Or increase the debuff cap ? Get the chance to attack twice and/or save TP before a weaponskill ? As long as it was a separate slot, why not both ?

You had gears that altered the way some abilities worked almost completely, or added a whole new aspect to them
The closest XIV got like that is the crystalline tools series ; and comes lv.100 there are certainly going to be useless because ilv & stats are what matters here.