Overwrite class in vendor

I would like to fix some issues that i have with the Phalcon\Config class and add that to the Incubator. The problem i have is that i cant find a simple way to overwrite the class.

As far i know i cannot just use the same namespace Phalcon and create a class Config because class Config extends Config ...

// composer.json
// ... 
"autoload": {
    "psr-4": {
        "Phalcon\\": "src/"
    }
},
// ...

// src/Config.php
namespace Phalcon;

class Config extends \Phalcon\Config
{
}

... well class should not extend it self :D

So i think this gona be a "second" Config class in namespace Phalcon\Config? Or is there another chance to get this working?