In my family my great-grandfather is known to have spoken Cree and Ojibwa as well as English and French. He wasn't indigenous. It was the language of trade at the time. It was a bit of a shock. Growing up I learned that it was perfectly normal a few generations ago for the white man to learn these languages, and I can only presume it was deliberately lost.
I think that what you're bringing forward is very important and I'm completely sold on the need to get there. But the first thing I want to focus on is the logistics. How we do it, until Douglas Adams gets his dream of giving the Babel fish to all of us?
On that basis, what's a reasonable notification period? How much time is needed? You talked at the beginning about being perfectly fine with notifying the House about your intent to speak in a different language.