A workaround to the canary is to every month release an affidavit that says that you have not received an NSL last month. The month you receive one you do not release one.
The entire premise of the canary, and this discussion, is that you cannot (currently, legally) be compelled to lie, you can merely be compelled to not tell the truth.
If they could, we would not be observing any changes in warrant canaries, ever.
Welcome to the real world, where armchair legal opinions don't matter. A canary is a way of communicating information about the NSL, which is prevented by the gag order of the NSL. The courts see through the canary for the transparent practice that it is. And guess what? These days they side with the government, not the recipient.