Not saying it would have saved him. But it would have been something easy for Jon to do. To say "Drop!" or "Turn Right!" Or even just swing his arms wildly to the right for him to move when he saw Ramsay draw back.Helpful maybe, easy doubtful. How would Rickon have heard Jon over the sounds of Jon's horse's hooves??? And without training, know what to do if he could hear Jon.
It could only have helped.