It would be smart if they use cash shop for "lost and found" or "preview"...

lost and found:
Its like seasonals you can buy or even legacy stuff. Maybe you can buy service to reforge a deleted weapon (if you throw away something by mistake)

preview:
if we will get marriage with x.1 you can buy it with cash shop and with x.2 you can marriage for free. This is smart, but also a bit tricky because it only works when they never stop developing "new" things, which means for x.2 they already need something new to preview.

Example: Sleipnir
Currently we can buy it from cash shop, but we already know there is an Odin Primal fight added in system (seen on fan fest and datamining), maybe we will get that fight with a nice story and then it "can" drop after beating him...