your spell creation idea reminds me of the "combo mater" from Sacred. Its pretty cool. THe only thing is i would require that the player has to have a skill for spell creation. So, if he has a skill of say, 8, he can do 8 figure things, making the spell more complex and powerful. also, there needs to be a chance of fatal error. I mean, if theres a chance of making the spell wrong, then there needs to be a penalty if you do make it wrong. And there would be varying degrees of penalty.

Another spell thing i would add under arcane is the ability to create undead. You would have areas such as graveyards and crypts that the player could create an undead army that would follow him. There would be a limit depending on skill, and you would be able to rise corpses too. There also needs to be a chance that if your skill in it is too low, the zombies will attack you. In fact, the whole idea of a penalty on low levels and the possibility of messing up spells seems pretty cool too me.