I'm almost hesitant to suggest this, because I can see where such a suggestion could also be used for evil. But hear me out...

What is, instead of just putting things up on the cash-shop -- which essentially robs it of any "cool factor", other than being whatever the item itself is -- you instead had to "unlock" cash-shop options?

Here's an example:

Right now, each expansion's Trials introduce a series of mounts (horses, lanners, wolves, dragons). Collecting them all gives you a sort of "super-mount". Well, what if collecting all of THOSE mounts, unlocked a new item in the cash-shop? Something you could ONLY get for having gotten all those items, but still in support of the cash-shop.

Now, obviously the knee-jerk reaction is "well, why wouldn't you just make that an actual reward?". But I view it more as an alternative to "just another thing tossed on the cash-shop".

Here's another example; if you clear Ultimate Coils, Ultima Weapon, or Alexander -- what if that unlocked the option to purchase a mount based on that content? Like a "Bahamut clone" or something?

That way, cool stuff doesn't feel "wasted" as a cash-shop reward. Because honestly, that new mech-robot thing? Maybe that WOULD'VE been cool, but because it's just a cash-shop mount, it has no "meaning", there's no weight or status to having it.

Just a thought. As a HUGE fan of Odin, even though I bought Sleipnir, there's still a part of me that hates using it, because I know it's "just a cash-shop mount". But if it was, say, tied behind an "Unreal" version of Odin? Then I'd be pretty stoked about it!