I think you're making a mistake. The primary intention behind warrant canaries isn't to shield you from legal retaliation, but to make it very hard to /legally/ force you to lie directly or by omission.
IMO it's questionable if a court in the US couldn't force you to continue signing it once they have the appropriate gag order, not signing the canary would be communicating to others you have a warrant with gag order and therefore not signing it would constitute speech which you aren't allowed to disclose as per gag order.