So in the TT game, one the main functions of your wizards is dispelling enemy spells.
I think this should and can be implemented in WHTW.
One way in which this can be done is to give all wizards the ability to be able to switch on and off a "block enemy spell" ability in their aura's area of affect. This ability could slowly drai the magic pool when it is turned on and should not always succeed. Some formula can be implemented where the higher the level of the wizard using this ability, the easier it is to block an enemy spell and the higher the enemy's caster's level attempting to cast, the harder it is to dispel etc.
This would be a very cool mechanic as it would allow wizards to protect a certain portion of their army agianst hostile spells.
You could also add a whole bunch of new abilities that increase dispel chance, increase dispel aura, slow mana depletion while in the "active" dispel mode etc.