B, I don’t see any upper limit to the number of substitutions, and can only think of advantages. As long as the workouts are replaced with similar duration and “in-kind” i.e. a Zone 2 for a Zone 2, a Zone 3 for a Zone 3… the ratios are going to be really really close. If you are an 80/20 subscriber, you can continually refresh your plan in this way. You have the base template for each week, but now you can swap that old RAn workouts (which is extremely effective) for a similar, but different Zone 4 workouts. You’ll never have the same plan again, if you want, but you’ll still be keeping to the plan’s structure and intent.
Ted, we won’t be adding all of our workouts to the free library for both practical and commercial reasons. Practically, it’s exceptionally time-consuming and expensive to create those FIT files one-by-one. We want the book purchasers to not feel obligated to buy an electronic plan, so we will continue to ensure that the book plan workouts are free, which will limit the workouts to <1,000. Commercially, it just reduces the value of the 80/20 Subscription if all the workouts are free.
David