If it does turn out that Regan votes to bale out Humza, then there will be no doubt in my mind, that it was all set up before yesterday's announcement. Still very risky though, as it would only need one SNP MSP to be "off sick" or one of them to "do a Kezia" and forget to press the button.
My prediction is that Humza will go. Sarwar's VONC will not pass, and SNP continue in Government. SNP elect a new Leader. Stephen Flynn wins and Shona Robison does the Scottish Parliament stuff until Flynn can become an MSP.