[InsainArcaneBirdbrain]

As cool as an idea this is, I'd have to say that it's probably better that such a thing is not added. 

My first reason is that as you pointed out, this system is prone to abuse. There are always people who will take every mechanical advantage they can get, and having exclusive item effects such as these would only skew things against those who can't make it to events due to timezones or life. It's not hard for a character to stand out if you put in the effort, exclusive mechanical benefits aren't necessary. Unique character traits are easily app'ed for, and everyone has access to this which makes it more fair.

The second reason is that if such items should come into existence, they should be available to everyone (looking at you tekagen ring). People have been wanting these for rp purposes for a while now, and making them exclusively GM rewards would kinda not sit well for a lot of folk I feel.