I like the idea of transporting a perk between two items of the same type.
I have for example an uber gear for a particular item type with a very useful uber perk that I don’t want to lose. When I see an item with better main perk and/or main stat, I might be tempted to buy it, but at the moment actually I am not. My main reason is that I don’t want to lose that good and useful uber perk. There is only a very slight chance that I get that same useful perk also on the new item.
And that is my main concern, why would I risk to lose hundreds of gems for first buying that item at grannies, knowing that I have to gamble afterwards with lots of pearls in the hope to get exactly that same uber perk again. what are the odds (4% - 7%), so that witholds me from even buying an item with better stats. Even with better stats, I won’t use that item, since I want that useful perk on the item during a raid!
If there was an option to transport a useful perk between gears of the same type or have a guarantee of 100% that I get exactly the same kind of perk I would not hesitate to buy that improved gear.
Another possibility could be introduced. When we use blacksmith and forge an item, we should have a second option, in case we already have an uber item for the same type of gear. Give us the opportunity to chose what we want to do. Decide whether you want to get an existing perk (pick the perk you want that another item of the same type already has) or get a random one. I don’t care that I need to forge that item three times to make it uber, at moment just before transforming it to uber the option should be to chose what you want as player.
I don’t care that I get an uber perk with slightly lower stats on the new item, stats can be improved. Transporting an uber perk is also a great idea, since it solves also that main concern of losing a great perk. I would not even care if the other item switches back to legendary perk.