One minute after president Cruz is sworn in, all of the JCS and their corresponding Vice need to be notified that they are retiring effective within 7 days.
Generals are almost entirely political appointees and are selected for their political ideology.
Name me one General or Flag officer in the last 50 years that was appointed to 4 star rank and the GCS based on solely on their combat record. All President Cruz will do is appoint those that agree with his particular political point of view. In that respect he will be not better or worse than Obama, Bush, Clinton, Bush, Reagan, or Carter. Nothing will change.