Allow clients to build their own training phases and workouts. Independence and having control over their own program is a lifelong skill.
Towards latter end of working with me, I like to teach my clients how to build their own training programs and workouts. Its an important skill to teach them so they don't rely on me forever. It gives them a sense of control and to be able to add this feature would be phenomenal. Otherwise the only thing they can do on their own is build a 'freestyle' workout and they cant even rename it or populate it into different days. Clients sometimes are frustrated that they can only do the workouts that I schedule out.