Small upgrade
add command:
/ac add <player> <alias> add a player - alias link
/ac remove <player> remove a player - alias link by player's original name, differ from /ac clear where remove from alias.
accountchanger.add allow to add a player - alias link (default by OP).
accountchanger.remove allow to remove a player - alias link (default by OP).

Bug fixed

Updates
Added commands

+ /ac list
+ /ac original
+ /ac alias

list list players allowed.

original list last alias in game and original name bindings of all players.

alias list original names and aliases bindings of all players.

Permissions

accountchanger.list allow list players allowed. (default for OP)

accountchanger.original allow list last alias in game and original name bindings of all players. (default for OP)

accountchanger.alias allow list original names and aliases bindings of all players. (default for OP)