I have worked on the default configuration implementation, the implementation is now located in the config-defaults branch.
The current tests are passing, i have not added tests for the implementation but i'll be sure to add those later.
The configuration now looks like this:

    'callbacks' => [
        // 'myCallback' => 'MyClass::myFunction',
    ],
    'defaults' => [

        'RULE' => 'allow', //Can be either `allow` or `deny`, anything else will set this to `deny` automatically.

        'CALLBACK' => [
            'name' => 'orUnauthorized',
            'args' => null
        ],
    ]

Adding a default rule doesn't add anything except overhead (unless I'm missing something), I think the general way of defining the default callback should be changed as well. I think we should fix the various callback issues (allowing instance methods for instance), before we tackle this issue