Sorry, I didn't read the PR description. I didn't understand the purpose of this.

If you want to decouple classes, you can provide defaults to avoid forcing the main app to define them while allowing custom configuration:

```ruby
Kpi::Usuario = Kpi::Clases.usuario_extern || Usuario
```

That way you can access the user class you want to use through `Kpi::Usuario` that will be defaulted to application's `Usuario` unless you define another class in `Kpi::Clases.usuario_extern`.

In addition, you can pass classes as variables, so using a string and `constantize` it's useless.