How to go over max protection and sharpness?

Hey, I would like my bosses to drop items which go beyond protection IV and Sharpness X but please note that above a certain level they items do not work. A protection IV chestplate is exactly as good as a protection XX chestplate. How do you guys counter this?

Also I saw that some servers, instead of having Sharpness and protection had numbers instead. For example an item would deal "10-20 damage". Do any of you know what plugin does that?

thank you!