Si Ren's plan was to have Zhang Qi use this opportunity to fake a temporary loss of her powers, just as he was doing.
In this way, not only could they successfully join the Southern Military Region, but they could also use their "powerless" condition as an excuse to recuperate within the military compound.
Otherwise, given their peak condition, although they could still manage to join, the military would undoubtedly assign them endless missions to complete.
Chapter 831