If clients are working out and a piece of equipment isn’t available they should be able to swap it for something else that works the same body part.
For example, if the Client is supposed to be doing a barbell squat and there isn’t a squat rack available allow them to hit a button that says “substitute exercise” and pop up with the library of exercises and have recommended options for them such as smith machine squat, leg press, goblet squat, etc.
This feature is available on CBum’s training app that a friend of mine uses and he loves it especially when a gym is busy or equipment is broken.