Replaying Baldur's Gate now, and I must say, D&D magic system is just plain awful! Seriously, you start with ONE spell. You cast it and you're useless until you sleep again. This was maybe fine when you were in a pen paper game and never got more than a couple fights in an evening, but in a computer game it's awful. Now you're level 3, and woopdydoo, you hav 3 or 4 spells (depending on house rules, magic items, etc). Yes, I know magic users seem to get overpowered at high level, but the balance is just wrong. All classes in a game (any that have classes) should be fun at every single level, players should never have to struggle with beginning of a game with the hope that it gets better later.
What I'd like is "Other" here. Not really a mana pool (the concept is just too stereotypical I think). Have a power/energy/fatigue pool. You can blow it all in a big inefficient burst of magic, or have a lot of smaller attacks. If you run low it will regenerate over the course of the fight as well, it's just there to slow you down and from being overpowered. No need to rest overnight, or an hour, or even 10 minutes. Absolutely you should be recharged by the time you get to the next fight. Of course if it's been a long day or you're badly hurt then it regenerates much slower.
That is a magic user should play somewhat similar to a melee or ranged fighter. If a level 1 fighter can shoot 20 arrows one after the other limited only by agility and stamina, then a level 1 magic user should be able to do the equivalent and be limited by power or stamina. And when characters of any class run out of stamina they're not useless they just need to slow down the attacks and catch a breath (no potions unless you're in a hurry).
I'd like to see fewer "spells" (or really just magical effects as opposed to cooking recipes), and they vary when being cast from low power to high power, or change effect to be single target or multiple target, a one shot or a continuous effect, etc. Don't burden the player with an overload of information about magic, some game manuals have 3/4s or more devoted just to spells. Keep it simpler and accessible.
Arcane and divine should be the same thing. If you are going to split into two then why not split into 3 or 4 or 20? Never understood that binary divide, too much like medievalism, exoteric vs esoteric, too much like D&D.
