If this existed my phone would be a smoldering pile of ash by now. I have had full on screaming fits with Siri during traffic because the engineers' bosses have such a flipping limited scope of building any extensibility into the app.
It isn't nimble.
It isn't flexible.
The only people I would allow on the Siri team are folks who use the app daily to do things without looking at their screens.
All of the jokey Easter egg shit would be the last thing they were allowed to mess with.
Vote for me as your new Siri visionary.