I haven't played yet (though I will a bit later), so I'm wondering how the shooting is? Is it a button for each skill, or one button to shoot, and another button (or two) to toggle spells? Cause if it's the second, I have a suggestion.
Alien Soldier (and Hard Corp for that matter) had a way to toggle between firing fixed (stand in one place while shooting, so 8-way aiming is more stable) and firing free (move and shoot, which makes 8-way aiming a little tricky).
Gunstar Superheroes for the GBA had each mode tied to a different button, with the free firing on the one of the face buttons (B and A) and fixed firing on one of the shoulder buttons (L and R). You could use your thumb for free firing, and your index for fixed really easily. With a bit of practice, it makes switching modes rather fluid and quick.
It also opened up a more advanced trick. When both buttons were held down, your firing direction was fixed, but you could still move freely. So you start firing with the fixed fire button held down to set the direction, then hold down the free fire as well to move so you could dodge or keep your fire trained on a target as it moved.
It worked cause it used both the thumb and the index finger in rather neat way. I don't how well it would translate to a keyboard though, but it's definitely worth mentioning.