Why So Many Key Item Slots?

[Enkidoh]

The devs still plan to introduce new classes in the future. Why would they do this if they weren't capable of expanding soul crystal storage? They're clearly able to add more storage space since we got some to accommodate for the new jobs and DoH, they're just stingy about it unless it's in the form of a cash shop feature.

Okay, I think you're being rather paranoid - SE have stated in the past that the inventory limitations are because of technical reasons and have nothing to do with the Mogstation, and everything to how the game has been coded (the Mogstation actually came much later, long after the game's launch). The database for your inventory and armoury chest is actually being constantly rewritten every ten seconds or so on the server, and thus because of this, if they made it too big, the database rewriting would end up taking excessive amounts of time and potentially cause server stability problems (this is actually proven by the annoying 'move' errors that occur if you try moving items around your inventory or between your armoury chest and inventory too quickly.).

This isn't the first time this sort of thing has happened with an online FF game either - in FFXI they had to restrict sales on the Auction House to just seven items at a time because anything more destabilized the servers. The fact is, all that calculating behind the scenes on the server is causing the inventory limitations - there is no magic wand solution, and it isn't a money-making thing either. SE are aware it's a problem for players though, and despite how it may seem, they will try and find some solution if and when they are able.