There are a lot of times where we need an option for a new start, therefore, having an option to delete ALL users who have added you should be an option when we change names.
This means they will not see your new username, the name could be a number generated username to the one deleted. The one deleting would have to re-add to make the one deleted to see their new username, manually. (After the delete)
We could also have an option to select friends on our list to keep but all others will be deleted once the name change in completed.
This would not be reversible once complete, both parties will see a number generated username and before completing the name change there should be an option to delete all none-selected friends to delete on ALL ends.
This would be equivalent to first starting out on Runescape, minus selecting the friends you want to keep. The ignore list 'could' refresh/delete also but that's not necessary.
sounds a little overly complicated, just add a favorite system to the fl and then have a delete all button that removes anyone not favorited.
pssst....we know who you are. Hail Sithis!