So it depends on the specific client, their goals and the situation.
You can definitely combine workouts as needed (especially the burner workouts), however, you want to make sure you don't overload your body too much. Adding too much can either cause injuries or delay you from reaching your goals.
It's all about listening to your body and making adjustments based on how you feel.
If you want to try combining programs and you feel great doing so, AWESOME!
If you try it out and it seems like too much, cut back because you can always build up.