Well, since this is Traditional I would go:
-1 Magical Dimension
+1 Change of Heart
Magical Dimension is awesome, but I rarely find myself running more than two in any of my Spellcaster Decks, in any of the two formats.
I know you have a theme going on but would't a Harpie's Feather Duster help here? would be better than waiting on a Dark Magician to be on the field. Giant Trunade and Heavy Storm are nice to consider as well same goes for Brain Control, Premature Burial, Mind Control.