Works for all versions with banners.

Tested 1.12.x without issues.

Allows players to create banners with more layers than vanilla. Uses existing crafting windows and recipes, no player commands, just the interfaces they are used to. Permissions can be assigned to limit ability to create better banners, including maximum number of layers and the ability to copy banners with additional layers. Does not have any effect on banners with six or less layers.

Installation

Just put the jar in your plugin folder, it creates a config file the first time you run it, with sensible settings. The config file has all the information needed to configure and the permissions list you will need.

Commands

/betterbanner reload - just reloads the configuration file, only OP can run this
/betterbanner ver - just lists the version number

Config Options

default: 6 - the number of layers someone without permissions can create
basic: 8 - number of layers someone with the betterbanner.basic permission can create
intermediate: 11 - number of layers someone with the betterbanner.intermediate permission can create
advanced: 15 - number of layers someone with the betterbanner.advanced permission can create

copy: none - Does not allow any copying of banners with more than 6 layers
copy: perm - Allows a player to copy banners up to the number of layers they have permission for creating
copy: all - Allows anyone to copy any banner

Permission

Ability to create banners with more layers is controlled by permissions. There are three (plus unlimited) levels of permissions for creating banners, limiting by the number of layers.

betterbanner.basic - Allows player to create a banner up to the basic: number of layers
betterbanner.intermediate - Allows player to create a banner up to the intermediate: number of layers
betterbanner.advanced - Allows player to create a banner up to the advanced: number of layers
betterbanner.unlimited - Someone with this permission can create unlimited layers in a banner

Better Banner