This post is only concerning the recently added "side" quests.
Let us consider what "questing" means in your average MMO (you may forget about FFXI here).
In most current MMOs, you can't fail to notice a pattern in quest design. At a camp intended for a given level range, a player will find a dozen or so quests he can handle at his level. Those quests will generally range from mundane tasks (kill x something, gather y something) to more interesting mini-games (catch that specific mob with this item, activate specifics items in the right order, etc.) and will tell you some part of backstory at the scale of the camp or the region, or even teach you a bit of lore. Doing all the quests at a camp of a given level range will eventually get you to the level required for the next camp, if not a bit more. Rinse and repeat if needed.
This pattern basically creates a way to level solo (or with friends, in a really small group) without any time constraint. You can log off or change activity at any time, and get back days later to finish whatever quests you were doing, if you feel the need to.
Of course, some players find this pattern repetition extremely boring. This is why most of the current games only use it as an alternative way of leveling, and not a mandatory path. This may be also why some players are weary of this kind of questing pattern as they may think it would be required to level (and believe me, it's really not in most recent games).
Final Fantasy XIV need multiple ways of leveling, if only because we all have multiple classes to level. I don't really see any downsides to using this pattern with the sidequests added recently. This could be developed slowly, level range after level range, camp after camp (we need low rank content anyway, don't we?), at the quest writers pace, in parallel of other content. Of course the whole system has to be balanced so that it doesn't allow a solo player to level faster than a group, but it should be competitive with solo grinding, at the very least. This should also allow the player to build a decent gear in the class he is playing (but of course, sub-par to the crafters items).
So, why not consider this, instead of adding those sidequests randomly in main towns? And make them a effective alternative (to dungeons, grinding, behest, leves) way of leveling?
(also I'm not sure I found the right dev-tag concerning side-quests)