Brizy PRO is going to handle only the visual website building part of your WaaS.
A Website as a Service platform is more than the tool you let you clients edit their websites with. You'll need a way to define the packs you sell, a way to process recurring payments and so on.
If you don't handle the set up of your platform yourself, there are plugins that can help you with that. You can use a service like WP Ultimo https://wpultimo.com/ to have everything up and running pretty fast.
They are the best in the business when it comes to building a WaaS on WordPress.