After some thinking, woulndt it be better to have a "fill up" system instead of a "cool down" one?; creatures unlocked/learned skills are normally at zero charge out of combat, they only start filling up its skills when it enters battle, when it gets out of battle its skills "fill up meter" starts dropping or goes to zero.( a casting time of shorts i guess?)
Why? skills cooldown means a warlocks enters battle with all the spells charged, ready to unleash hell a few turns and be picked up again to safety. Having a fill up system makes units stay for a while in battle until skills are charged, and a powerful skill will never be used from a just dropped fresh creature, it will have to stay for a while exchanging blows until it can use it (if it survives).
A dirty trick would be to "trigger" all creatures skills/attack cooldown (like they had been used) when entering battle so it has to wait for it to cooldown before using them; same result as filling up but less programing involved
Pros:
more strategic and somewhat more realist figths
Cons:
programming?