My fear is simply that, when it comes to one-of-a-kind items, I like having a little more room to breath. Take the Lightning Returns costumes, for example; a lot of players are probably like me, in that they're only really focused on a single character. Wouldn't it be nice, though, if you got the full Male clothing set, you could also get the full Female clothing set for an alternate-character, that you might not otherwise have played? I'm not even asking for the items themselves; just the ability to use their appearance for Glamour.

Or as another example, take rare/hard-to-get items like the Armor of Light or Moogle Weapons; they're items that might not "fit" your current main-character, but could be cool to use on a character who might never set foot in a Raid.

You make a good point about tradeskills, though, and I could definitely see some items -- like the Relic/Artifact gear -- remaining Character-specific. For rare-drops and retired-items, though, I'd just like a little more room to breathe, you know?