Additional Dupes of 4\* Characters give 5 Masterless Starglitter at least, whereas Weapons only give 2. We should totally be able to refine all the extra 4\* Weapons into one copy that is already R5 for an additional 3 Starglitter.
That would make sure that you also keep an R5 copy of each weapon first and still let you get a full Wish back when getting another duplicate. Noone needs 30 Dragons Banes ffs....
Let us refine an R5 Weapon with Spares for more Starglitter