And if it were possible to create an ability that's the opposite of what mages do, so that it increases the cost of enemy spells, that would be amazing!
If you put in a little more effort, you could move dragons far away (the light elves have boring dragons), lower ents to level seven, adjusting their stats and giving them a model of classic ents (such mods already exist).
Lower unicorns to level six, adjusting their stats.
And the newly created pegasi to level five. Flying, magic cost increase. It should look pretty good.