The problem with this (aside from that we've all had to stop Shantotto destroy the world every month - she's one of the things that contribute to Vana'diel having to be saved every other day) is that Meteor is already a spell that's been used in the game before, notably, by Shantotto herself.
Ultimately, I'm not opposed to having to farm the thing, but certain things are just more epic when they are quested, like Sleepga II.