Today I'm glad to tell everyone that I finished work with this feature and already pushed full patch to our repository. That means that new feature will be on servers with next update!
Almost nothing changed since my last preview from players side. I only added price for using this option. The price is:
cost = 1000gold*((Quality1+Quality2)/2) where Quality1 & Quality2 - quality of item-prototype & item-target. Pure quality is 0, common is 1 etc.
Have fun!