Wither is coming in 1.4 update and we all know it. But I'm proposing some changes.
-Withers shouldn't be able to eat what's listed on the list of blocks
-Withers should drop 500 experience worth of orbs on death.
-New drops: Wither's Skull (You can place it on wall. It's a trophy! Also, you can wear it. Have blur, just like as if you're wearing pumpkin, but blur is different.)
-New drops: 10x Wither's Bones (Needed, along with Obsidian and Eye of Ender, to craft Wither Armor)
-New armor set: Wither Armor (As effective as gold armor, but never breaks. Comes with Projectile Protection III. Very hard to get resources to craft it.)
-Wither is able to spawn on Peaceful because it's a boss mob. They do same damage as on Easy.
List of blocks that Withers should be unable to eat (For anti-griefing purposes)
-Wooden Door (Wither will attempt to bash down doors, like Zombies)
-Iron Door (Wither can't break these)
-Minecart (You will be able to push Wither into Minecart, making it an easy kill.)
Wither armor will be the first ever special type. It gives you high resistance to arrows. It have infinite durability. However, they offer the same protection as gold armor. You have to go through the intense process to be able to obtain the armor set. Crafted using Obsidian, Wither Bones and Eye of Ender.
Wither also drop its head (Wither's Skull) on death and you can collect it. That would make it the second trophy, with the first being Dragon Egg. It's also renewable, as Wither will respawn. Can be placed on wall or on item frames. You can wear it, just like pumpkin. While wearing, most mobs will be afraid of you. Creepers will run from you but still attempt to explode if you get close. Pigs, sheeps and cows will try to run from you, making hunting a bit trickier. Wolves and ocelots will attempt to run from you, except tamed Wolves and Cats. This making taming difficult. Villagers are unaffected although will be a bit afraid of you. Some may won't let you trade with them.
Withers, unlike Ender Dragon, do spawn although very rare. Finding one is like mining for diamonds. And they also can respawn every 50 in-game days, or 1,200,000 ticks, so it's a very long time. The generation determines where Wither will spawn and sets the respawn point of Wither. The game checks every 50 days if the Wither is dead, and if it is, the Wither will respawn.
A few things.
First off, considering the enderdragon drops 20k exp a mear 500 exp seems like nothing more then a mere pittence, not to mention the wither is stronger then the enderdragon... if you fought it with a mod you would know that. Next for the trophy item, i think a pile of black bones with the wither head on top would be better then just the head, also it should have a unique property to it like the enderdragon egg does. And next, that armor seems kind of pointless, its only real use would be as a trophy and we all ready got one of those so... i would just scrap that idea to begin with. Next, there was already a good suggestion for when and where a wither would spawn in a diferent thread so I'm just gonna skip this. And last but not least my final point to make as far as your suggestion goes, since when has any mob gave a [email protected] about anti-griefing laws, i mean just look at the creaper. not to mention the damnage that a wither can do to your place is minimal every shot it fires only destroys one or two blocks, not all that much really.
After reading some feedbacks, I'm making edits to the suggestion. Wither Armor will come with Projectile Protection III. They can't be enchanted. Also, Wither Armor is craftable, but you will have to go through the intense process of gathering resources. Wither Armor will have unique texture.
Methinks the Wither will be in the overworld. Why else would it bomb the %*()#&% out of animals. In addition, I think most of these changes aren't 100% necessary. Let us see what the Wither really is like...