What about something to find and collect through Eorzea?

[Munba]

Some other ideas,

Mog Hunt!
You'll have to find all the moogles hidden (invisible) around. Every mog will give you a reward and will tell you a riddle to find the next one (the sequence of every next mog wil be random for every player).. and when you click in that spot, it'll appear. When you find all, you'll have a big reward... maybe the possibility to access to Moogle Village

Merchants Extravaganza
There are several special merchants around the world (also in hidden places). When you find them, they could be hired to become your retainer. Every merchant will have unique skin and stand (when you create the shop stand). And they could have some special abilities too, like more inventory space.

Full your home (when housing will take place)
In the same way of merchant extravaganza, you could find some particular people around the world to hire for your house. You can recruit them by quest or paying. Every npc will have its own profession for your house (smither, etc.).