I am not sure why this was removed from the game, whether it was actually causing problems with code or if it was removed simply because it wasnt intended to be in the game to start with, but either way I believe it would be good for the game to have it put back in. I had only upgraded two uniques before the patch, and neither of them turned out that great, but being able to do it excited me and made me want to play. There are several reasons why I think upgrading uniques should be allowed:

• It is unique to Wolcen, as far as I know, which is automatically a bonus for the game
• Players enjoy it. From the streamers I have watched that have done it, they seem to agree that this bug is one of the best features in the game
• It provides a worthwhile sink for Production in the endgame
• It allows uniques that you find when youre leveling up to continue to be useful later on
• It allows for more customization in the endgame
• It provides a way for uniques to compete with legendaries in endgame

I am not aware of any upgraded uniques that were game breaking. They are just marginally better and customizable with crafting. If it was somehow causing problems with game code, then by all means get that sorted out, but please consider putting this feature back in to make the game more enjoyable for the players.