Giant Zombie Spawning in Zombie Village Sieges

While giant zombies are currently in the game, they have no AI, nor have they ever spawned naturally in Minecraft.  I'm thinking it would be cool that if a zombie siege occurs in a village that previously used to be a zombie village, then maybe have the giant zombie spawn in with the siege (but only a one time occurrence for that specific village).  I don't know how doable this is, but I thought I'd throw out the idea.  In terms of what AI they would have, I think just having one similar to a zombie would be enough, just have an abnormal amount of health and strength.