"Easily" might be overstating it a little. Dismemberment alone would take completely redoing the work with the modeling to give Ryu new animations and give the enemies animations as well for the removal of their limbs, plus new attacks for them to do once they've lost those limbs, and then new dialogue for all the enemies from them reacting to losing their limbs.
Plus they would need to increase the difficulty because lost limbs=OTs being activatable all the time=clearing rooms much faster. Not to mention a complete revamp of the Ninpo system due to the addition of new Ninpos. That's a lot to fit into one patch, and the limb part is anything but easy.
It strains the mind a bit don'it? You think you're all alone... maybe I come down the chimney, bring presents to the good girls and boys. Maybe not, though. Maybe I've always been here.