1.) Modding tool
2.) Allowing you to place more than one trap at time
3.) More spells I'm a mage, so i always want more spells
4.) Romance. I don't exacly feel the party without one...
5.) Like someone stated above, more terrain diversity
6.) Having elemental spells actually ma a diffrence like in Original sin, when rain make you soak, and lessen dmg from fire.
7.) Having options in the dialog's that allow you to use spells, for example during talk with a guard, you can cast mirror image, and order him draw attention from you. Okay, mayby not the most ideal example, but you understand what i say, right ?
8.) I know there is a reputation, but it would be nice, to have some light side/dark side points. The abillites of you character could wary depending on what side you swing.