Commands:
/nick - nick or unnick yourself
/addnick <name> - add a new nickname to the list of nicknames
/removenick<name> - remove a nickname from the list of nicknames
/realname <nickname> - Shows the Players that currently use this nickname

Permissions:
You can modify the permissions in the script options.

nicksystem.nick - Allows the use of /nick
nicksystem.addnick - Allows the use of /addnick
nicksystem.removenick - Allows the use of /removenick
nicksystem.realname - Allows the use of /realname

Extensions in work:
- MySQL Support
- Bungeecord Support
- Autonick on join
- Autonick item

Dependenecies:

Skript: https://dev.bukkit.org/projects/skript
Skellet: https://www.spigotmc.org/resources/skript-java-addon-skellett.34361/
Lib's Disguise: https://www.spigotmc.org/resources/libs-disguises-free.81/