Overwrite Namemapping Configuration in Runtime

Is it possible to overwrite a mapped objects className within a script during runtime?

 

NameMapping.bla.element.this.className ="newClassName"

 

Sadly this doesnt work, it only overwrites the classname in the HTML document.

 

Is it possible to overwrite the className within the mapped objects NameMapping tree? 

 

I know there is a workaround with a project variable, which you can set during runtime and use it as namemapping, but I am curious if its possible to overwrite the configuration during runtime