I know remapping the Fn key alone seems like its impossible, but what about the actual combination?
FN + c, FN + V and FN + a to be remapped to the ctrl + C, V, A.
Not only does Fn usually not generate a usable keycode, but it will also not generate a usable keycode unless used with specific keys, as determined by the hardware. It does not generally act as a modifier. You can try to use
Fn is a hardware key, so there's no way to remap that except for some hardware that allows generating a keycode for it.
If you only want to swap Fn and Ctrl then look for the function in BIOS setup, most laptops that have Fn on the left of Ctrl have this option