So, basically what you are proposing is that almost all spells should have such a high cost that you will have to wait several turns in order to accumulate enough APs in order to cast them? But wouldn't the fights become so very boring when you basically have to do nothing and just to wait through many turns in order to save APs? And what would happen if raising all the stats and having the super gear equipped you manage to get a character who has 15 APs every turn? Such a character would be way to overpowered and would be able to cast armagedon spells without any restrictions.
Let me just bring an example. I have now a witch (level 5) who has something like 7 APs. A wolf summon is very useful for distraction of enemies and deals a decent damage (plus bleeding status). A wolf summon is a level 1 spell, costs 4 AP and has a cooldown of 4 turns. This means, that basically only one wolf can exist at the same time during the fight (the old wolf is usually dead before my witch can summon a new one). So, now if the cooldown is gone, how high would you set the AP costs for a wolf? If it is less than 7 AP, then my warriors do not need to do a stroke since my witch can spam wolfs every turn. If it is slightly higher than 7 APs, ok, let me just go and check the merchant or just wait for the next level up so that I can increase my speed/constitution and we have the same problem as before. Should it be more than 10 APs? Probably not, since it is just a level 1 spell...
So, I think cooldowns are really needed as a restriction...
