Gearscore in WoW worked because each slot was based on an algorithm to determine how many stats it has.

Example Ilvl 110 would be weighted for 300 stats, and Ilvl 120 for 330, etc (or 110 and 120). AGI = 1 point, 2 Attack = 1 point etc. But Ilvl 110 bracers and 110 chest wouldn't have the same # of stats (Chest would have more, stronger piece)

FFXIV gear currently doesn't seem to operate on any linear function currently other than weapon's seem to Tier off of DPS but their bonus attributes seem to just be randomly added as a set function.

They already have a tier function in the game (Max Level Tier4 materia's compared to each other can determine relative gear weight) to determine the worth of each gear piece but as I said currently SE doesn't seem to follow any function when weighing the stats on each gear piece.

That would have to change if they wanted to use any form of gearscore that matters for well, anything.