Alright, I am going to jump into here now.
First, this went from a decent discussion to a discussion where people are even going to mention arguments that has nothing to do with te actual suggestion. With causing in the end people appeal to emotion.
An appeal to pity is never a good argument, it is even useless, there is no need to say things like this
Funny you would say that, seeing as you got your Prot IV armor today
. ( Note that the quote was a randomly picked one. )
http://blocktopia.net/forum/threads/concerning-arguments.1500/
Then about the armour, which seems most of the issue here.
Personally, I don't see anyone going to swim in lava with the armour to make benefit out of it, I might see people jumping people from high heights, but aren't we all doing that already? Some might on land, but already a lot do on water whenever they see a spot. I really don't see how that is an issue.
People will probably use it majorly for pvp, but we have potions to outsmart your opponent and enchantments yourself!
Mistakes are easily made, and armour isn't forever!
Further, in Minecraft you have a lot of freedom. If people want to spend of their time next to a grinder, it is their choice to. Only rule on our server about grinders is that people are not allowed to stand next to grinders as Away From Keyboard.
Some people have said in the discussion that potions and enchantments ruin pvp. Maybe it ruins
your way of pvp, but if you remove potions and/or enchantments it ruins
diversity in this game.
So... I am not even close to implementing this plug-in after this discussion, and I only see replacing the problem.