1) Perks, especially: Cold Steel, Reflection, Magic Drain, and Dark Regeneration. They are extremely useless in the vanilla game (even though the idea itself is quite good). I would like to see them strengthened.
2) The ability to have multiple summoned creatures in battle at the same time (elementals). Multi-summoning, like in the third game.
3) The ability to continue the battle with summoned creatures after all non-summoned creatures have died. Again, just like in the third game.
4) Fixing the specializations of Sorgal and Talanar. Otherwise, they are completely useless.