Well I have an Idea on this predicament (XD) Actually I'm thinking of implementing this system on my upcoming map . . . well maybe not. . .yet. Anyway~
I was thinking of a system that you can set your currently usable active abilitites.
Ok an Example:
You have a hero. . .
Name: Mage
Abilities:
Fire, Thunder, Blizzard, Aero, Flare, Giga Burst.
So . . .
Let's say you have those abilities and you can only have 4 abilities at a time. Let's say you set Fire(0,2), Blizzard(1,2), Thunder(2,2), Aero(3,2).
So you want to set let's say set Giga Burst. You will be given an option (Maybe via a custom interface like an inventory system or something) to set Giga Burst instead of Aero to (3,2)
So then the sequence will be . . .
Fire(0,2), Blizzard(1,2), Thunder(2,2), Giga Burst(3,2)
Also . . .
I'm thinking of a having a sort of, Ok I'll name it "Ability Deck". Basically you have 2 ability decks where you can set the abilities you want to use. Then you can interchange them(maybe via pressing escape)
Ok Example:
Deck 1: Fire(0,2), Blizzard(1,2), Thunder(2,2), Aero(3,2)
Deck 2: Haste(0,2), Vanish(1,2), Stop(2,2), Gravity(3,2)
Now let's say you are fighting and you have deck 1 as your active deck, which means you have the abilities you have set (Fire(0,2), Blizzard(1,2), Thunder(2,2), Aero(3,2))
now you want to use the other deck. You press ESC(maybe). Voila! you know have the abilities in deck 2 (Haste(0,2), Vanish(1,2), Stop(2,2), Gravity(3,2)
Well that's my Idea. Just wanted to tell you guys. It might not be File Size Frienly nor will it be code friendly but just wanted to let you know hehe.