This would cause such a shit storm that the Tories would never been seen as a credible option again. ECHR is embedded into the Good Friday Agreement. This would throw the whole process up in the air. That would antagonise not only the EU but the US also. They have been threatening this since Johnson. I could easily believe they are crazy enough to go through with it right at the end of their term. Labour would put us straight back in again.
Inews has done an article on just this. It looks like they want to finish off the job of smashing the country to pieces before they are kicked out.