The lava tube idea is intriguing, the heat from the lava pools would be an immense bonus if we're trying to build a self-sustained enclosure, and I imagine more cost effective too!
I did a double-take when I read the part you mention Elon Musk as a boring company, then I realize it's a different type of "boring" lol!!
We will just have to wait to see how it develops but it won't be long now.