So, we are keeping 4510 instructions for C65 mode, but we will have an option to tell the CPU to operate in 6502-only mode. This will probably be the default in C64 mode, unless the program asks for the CPU to be super-fast, in which case we will take that as informed consent for 4510 opcodes. However, it is a bit interesting, as the c64-mode kernal uses 4510 opcodes for the floppy drive interface. As a result the whole thing will be a bit fiddly for us to get just right, so that everything works as expected. We'll probably also have a hypervisor option that allows forcing the CPU to one mode or another, so that the end user will be able to control this behaviour completely, and M65-enabled programs will always be able to use the new opcodes.