Whatever refrigerant they chose it will likely have a GwP 100s-1000s of times worse than CO2 and if some part of the refrigeration circuit fails the entire contents of the tank could be vented to the atmosphere. The green crowd won't like that. Also, people may eventually save money using heatpumps, government won't like that so what better way to ensure money keeps circulating than to invent a new profession & force people to use said newly invented profession's services by law.
I am a cynical bastard but been around long enough to know the government hates nothing more than people not parting with their money. Once a significant portion of the population manages to reduce their energy costs through solar panel / heat pumps they'll try and claw back their savings.