In Oblivion your hands were used for swords and shields ect, and spells did not take up a hand. ie: You could use a sword and a shield and be able to cast a spell at will.

Advantage- A melee focused character did not have to switch out his sword or shield when a spell was needed

Disadvantage- A magicka focused character did not use his hands often because spells do not require hands.

In Skyrim this was changed so that spell-casters needed free hands to cast spells and could cast two at once.

Advantage- A magicka focused character could focus entirely on spell casting (dual-casting)

Disadvantage- Melee focused characters (That are either two-handed focused or use a shield) have to swap out a hand to use their magicka.

A combination of these two mechanics could keep both advantages and lose the disadvantages.

I would suggest that the two hand system is kept, allowing magicka users to use to hands to focus on spell casting along side an extra spell slot that did not need a hand. This would allow melee characters to use magicka without swapping out a hand, while allowing the spell caster to have an extra spell on hand (which is useful considering the amount of spells that the player may want to use in a given area) without having to fiddle with the menu to access a secondary spells that is still useful in some areas (such as turn undead) but is not a primary damage dealing spell.

I'm interested to see what others think about this idea.