I've been thinking about it. Raise/lower or buffs for units or champs, or even cities...
What about adding a button somewhere in the UI* with the "RE-CASTING" skill? This is, casting again the last used spell, whatever it was.
*The natural place would be at the side of the "SPELLS" button
So you don't need hotkeys bars and nothing else, just hit that button and last spell is casted.
If the button said what was the last casted spell, that would be GREAT.
