The ability for an iPad to support multiple users would make it a compelling HomeKit controller.
1)each person using it would be able to see their upcoming things just like the HomePod is supposed to be able to do
2)each person could easily have different permissions
3)with a charging dock it could essentially function like Amazon or googles smart screens but with the added benefit of being totally portable.
I know apple would prefer every person in a family be using their own iPad but with just some effort this could be in addition to your individual device.