I believe that fusion and revival feel better as things to have "in stock", as opposed to something you sacrifice from other areas(ability learning) in order to have. My idea to bring this about, without going back to the old item system, is:
-There two types of currency.
-Type 1 currency can only be spent on ability learning.
-Type 2 currency can be spent on anything.
-Fusion and revival have their costs reduced in exchange for only being purchasable with type 2 currency.
-The total amount of currency dropped is reduced slightly, but the overall value(if you use fusion and revival) is potentially higher than before.