Ideas: Numbered structures (tower 1, tower 2, etc.)
Defense: SP (structure points) for each structure part. Add more SP by reinforcing that area of the structure (extra layers, walls, repairs)
Windows require Aimed Shots, but if successful, damage the inside structure, reducing Status of building, and chance of killing NPC’s.
Offense: Siege weapons (arrow/stone ballista's, fire, magic, hammers do +5 dmg to stone structures, axes do +5 damage to wooden structures, flaming arrows do +5 dmg to all structures.) Damage from inside out causes 2x damage.