How is that better? Not only will everyone still wear the same thing (BiS will always be seeked out, this will never change except through vanity slots), but the item slot will no longer be of any use as the item will always be there.
You might as well just build those stats into the character and remove the slot all together...
The progression model is made to allow the carat on a stick syndrome that developers can use to manipulate players into playing content (repeatably as a time sink). By giving gear that's irreplaceable, its removing the powers that the Dev's have over the user base.