Few days ago we started working on Italian Fatturazione Elettronica and Revenue stamp on Invoices. Both features are crucial for companies based in Italy but we didn't want to make Settings page bigger for our non-Italian customers. Considering that we also have to add a similar plugin for Finnish companies, we invented this new concept: plugins!
Every plugin can be activated and deactivated individually and has its own requirements and version number. When you activate a plugin, Billing Extension installs it and allows you to customize it from the usual Settings page like you can see from the example below.
This way you can add to Billing Extension only what you strictly need.