The illusioner illager mob has not yet been added to minecraft because he is incomplet
This is an idea which aims to improve him, make him fit in more with the rest of minecraft.
Firstly, he loses both his bow and his ability to magically cast blindness at the player.
Instead of these, he has a magic wand, and magic reagents.
Whenever the illusioner is about to attack the player, he holds his wand in his main hand, and a magical reagent in his off hand. This reagent is randomly selected from amongst Azure Bluette, Lily of the Valley, Tulips or Wither Rose. When he attacks, his wand will fire a projectile which does no direct damage, but produce in the victim either Blindness, Poison, Weakness, or Wither, depending on which reagent he has in his off hand.
If there are other hostile mobs in the vicinity, the illusioner may choose to buf them. He does this by holding his wand in his main hand, and a magic reagent in his off hand. The reagent is chosen from amongst Allium, Cornflower, Oxeye Daisy, with the projectile producing Fire Protection, Jump Boost, or Regeneration respectively.
If the illusioner has made himself invisible, all of his duplicates will appear to fire projectiles when he does.
When an Illusioner is killed, he has a chance to drop his wand and flower, or his cloak of illusion.
When the player is using the wand, it can produce any kind of magical status effect which a suspicious stew could produce, and as it does so, it consumes one of the corresponding flower, which must be in the player's off hand.
When the player wears the cloak of illusion (in the chestplate slot) it makes him invisible, and produces duplicates. Whenever any mob (or other player) has line of sight with the player wearing the cloak, and their "eye-line" happens to be aimed in the player's direction, it's durability slowly but steadily goes down. The cloak provides no armor protection.