First of all, thank you for sharing scbFramework with us!
I'm looking at the Smart Archive Reloaded plugin to understand the basic workflow with the framework and I'm wondering why did you create a register mechanism in the AdminPage class instead of just instantiating an object and using it that way?
Does it have to do with keeping the admin functionality in a separate file? What is the philosophy?
Also, which functions did you choose to name with a leading underscore? I see not all named that way are private and not all private functions have such a name convention. Is there a different rationale?