Best part is, SE has a precedence set with FFXI:

Gobbie Bag Quests (no rl money needed)
Mog Satchel (Came with buying a security token)
Mog Sack (Speak to a moogle..free space..and it scaled with your current inventory, so more spaces you get with gobbie bag, more sack and satchel space you get.)
Mog Case (Logged in after update..free 80+ inventory increase.)
Porter Mog (Trade almost every rare/ex etc gear to the moogle, so essentially more space.)
Mog House ( Storage system granted additional 80ish spaces when you decorated it at the cost of some of your mog house slots.)

However people want SE to ignore what they did in FFXI.