For example, extending sprite class with some custom "methods", which could be accessed through events and actions. As far as I understand behaviour system has exactly this function. May in the feature it will be possible to write nested event logic with visual editor inside an object type, which could be accessed like a method.
Another example is defining a new/custom class type. But again, behaviours and plugins are the answer.
May be there are some good practices, how to structure event logic, so it resembles some OOP concepts.