Grails Service

layoutService.groovy

 public list(){
        Layout.executeQuery('from Layout where user is null')
    }

    public list( User user ){
        Layout.executeQuery('from Layout where user = :user or user is null', [ user: user ])
    }

Not sure I agree that overloading methods would 'change the core nature of the language'. Make it possible to do so, but not mandatory. Problem solved.

I disagree that dynamic argument styles are more elegant and is more elegant. Method overloading may result in more methods (more lines of code), but each method would, in my opinion, more elegant that the uber-method you would need to handle this with dynamic/optional arguments.