I plugin that you can add permissions to it so if you like right click a sign it will do something, I was thinking of putting signs down so I can make it so they pay an amount of money and gives them a rank when you right click the sign. I know ServerSigns works like this but it wont work for me because PermissionsEX. In PEX you have to type the command /pex user <username> group add [Group]. So when they right click the sign I cant put their username in because not everyone has the same username...
ServerSigns and PEX work together. We even had a sign to promote guests to builders. Try /svs add <server> pex user <player> group set Builders . Obviously replace builders with the group you want to promote them to on each sign.
Are you sure that plugin does not have a specific code which replaces it with the player's name? e.g. '/pex user &p group add group', and it replaces the &p with the players name.