Master and secondary workouts
My idea/proposal is to be able to create a 'Master' workout, then if you copy this workout and place it in your calendar say 10 times (secondary workouts) when you make a change/update to the master workout this is automatically pushed through to all the secondary workouts. Currently I believe you would need to edit each of the 10 workouts individually.
A further development of this concept would be to have recurring workouts, with perhaps the possibility to increase volume/intensity by X% for each occurence to fit in with periodisation.
When you make a change to a workout in your library, all instances of that workout used in your training plan library receive the update, as well.