Even this would not be 100%, because you can use sendMessage via the Scripting Library. We're tossing around several ideas internally, but it'll be some time before they're finalized and implemented.
Also, as Paul mentioned, we can't construct a list of messageKeys from scripting invocations, because
system.perspective.sendMessage('UPDATE{0}'.format(self.getSibling('TextField').props.text, payload={}, scope='session')
is totally valid, and would result in different message keys when in use.