Actually, it seems to go not that straight:
Meteor Staff -> Blizzard Staff -> Lunar Flare
And I'll stick to idea of using luminite ore as ammo. I don't know why, but I really love it... Especially because it looks like some hight-tech material or future quicksilver (mercury)...
Really, it would be awesome, especially considering it's power.
Stars would be good, but I see two problems with them:
1. Easy to obtain, as for this tier of weapon. You know, if it would be luminite ore, then it would be obtained in large equntities, but still hard to do so. Obtaining Stars is for me actually even more painful than crushing ML.
2. Then it wouldn't look so cool, as it would be upgrade to Star Cannon, which - while unarguably powerful - looks... not badass