In the new EFL widgets we restricted style set on the layout only before it finalized,
some there is still some cases that need to be styled after it finalized.
Layout factory for instance,
style value could be existed in the model data,
so we giving theme_config API to set klass / group/ style string.
layout factory can set this style after the object creation, as it need to call the efl_super on cached_factory and widget_factory.
solving the issue is not difficult, but the way of doing it need to be discussed.
one way is giving style_force_set Method that allow style set after finalize but user has to understand style changed and every property on the object will be changed also.
the other way is allow style changes internally, so factory may allow to set the style of layout repeatly.
second way is more safer I think,
but it makes user customizing on the factory quite harder.