In short, you are asking that devs add a mooglestone prize in Wondrous Tails.
The moogle event is a lure to push experienced players to make content they normally avoid playing and as a result new players find group more easily.
Other than that the event gives something to do in a flat period.

If I can just do some expert / levelling roulette to acquire mooglestones the meaning of the event is lost.

Btw, I see platinum MGP card as reward for my W. tails card.