uhhh freezing + lighting does extra damage sounds stupid (plus im not exactly sure if crystallized water is a good medium for electricity) , elemental weakness + elemental attack makes more sense to me . That would go back to good old diablo with necro hexing people and then shooting them with magic

On the combo sides ,i really like the idea from Dragon age and NWN when wizard can cast grease spell that can cause enemies to slip and then fire ball to make enemy burn longer or cast blizzard to take out flaming area .