I think a simpler solution should be in order. Whenever a drop button is pushed, a pop up that advises against trading should come up.

"Do you want to drop this item? Be aware that you drop at you're own risk. There is a chance you may loose your items permanently with no compensation."

I like the ability to drop items. I think all weapons however, should be non droppable, unless they are for fun. Yes, it's unfair to give out a free Melee that can rival an expensive Melee or an EC Melee. I think holiday shops should be the only place to get those special items.

Any way you look at it, a real trade system kills the game.

So either make the warnings noob-proof and in players faces everytime they drop items... or only enable job and minor items to be dropped.