Exactly !!
I like it. Immune to X-bow, cannons, and archer towers(basically) but very vulnerable to Tesla (metal shield), bombs, and mortars. Also, if you plan your attack badly and they face away from these defenses, your army gets wrecked! These would be a great higher-level dark troop that's both powerful if used correctly and takes a great amount of skill to master.
Shameless Personal Bump, don't hate, but still like the idea.
So it is able to completely defend itself from one defense at a time? I like that idea.
I guess it would be more like a quarter of it's body is protected from all defenses, which ever way he is facing. Think Link in the old NES Zelda games.