The reload instance switching code should be centralized in ApplicationHandler impl (i.e. rename existing ApplicationHandler to ApplicationHandlerInstance and introduce new ApplicationHandler that contains support for instance reload and delegates to current instance).
Remove ConfigHelper API. Instead give access to all the configured listeners in the container and provide a composite container listener utility class as part of the API which container providers can use if they want.
It should be possible to register multiple listeners via property. The property should provide the same capabilities as registering listeners via resource config as providers.