In the manual, in R1, it says that “if you are swapping out an entire subsystem of either item 1 or 2, you have now created a second robot and are no longer legal”, and later, “Teams may not switch back and forth between multiple robots during a competition.”
My question is this: Can you switch back and forth between multiple versions of just subsystem 3 during a competition and remain legal?
Yes, this is legal.