Enchantments on defensive units?

I read the list of ruled out ideas, and I don't believe there's anything in there regarding this subject. Maybe ammo modifiers, but this is a bit different. We have a spell factory for offense. Why not have one for defensive structures...an Enchantment Hut...or Wizards Den or something like that.

Hitpoint Boosts
Damage Boosts
Range Boosts
Sticky Ground (slows movement for attacking troops)

As far as strategy defensive spells like this would make potential attacks less predictable, and would add to the overall fun factor of the game. Everything can't always go exactly as you plan it. Armies would have to become more flexible which would increase attack variations.

Anyone else have an idea or opinion to add to this concept?