Fortunately, I won't have any problems because my username is unique after sorting out my NA/PBE/EUW accounts, but for players that _do_ have to change, is there any chance Riot will do anything to prevent names being taken by newer or inactive accounts?
IE: Someone on NA has had their level 280 account with the username "Bob" for 10 years. Someone on RU has a level 5 account that they created 3 years ago with the same username, and they haven't touched it since the day they created it. Is the NA player just shit out of luck because that player is never going to log back in?
It seems like you could just wipe the slate clean, and give usernames to whomever claims them first. That way people who currently have unique names won't have an issue, players that want to change their usernames can, and players who have their names taken by inactive accounts won't be fucked over because that player is never going to change it. It also adds less confusion on Riot's end with making sure emails have been sent out.
Alternatively, have everyone create a Riot account, have players link their league accounts to it, and just retire being able to use their league account to log in.