I had to do some research to see how I failed to see this before.
It turns out that, just as I remembered, Cruz was put forward as a possible name to replace Boehner. I just did not recall anyone making an issue of him being a senator. (But they did.)
So, actually, there is no REQUIREMENT for the speaker of the house to be a Congressman. But, it just so happens that ALL speakers have been picked from Congress.
This means, in theory, Cruz COULD be speaker, though it is very unlikely to happen. Regardless, I think we should be looking for someone to replace Ryan as speaker. We could probably do worse. But we can almost certainly do better.
No House member would ever vote for a non-House member to be speaker! Theoretically possible or not!