Essentially you are asking whether Tesla can decouple FSD (the software) from HW3 (the hardware). But why would they break those out separately if you can't actually take advantage of the hardware? It makes sense for new cars off the line but you're talking retrofits. There's no upside for Tesla to do that. The cost isn't just the hardware, but also technically includes the labor and SC time to perform the installation and testing. SC's are already overloaded and working through a retrofit backlog. Why would they add to that?