I really like the idea, it reminds me a bit of Goalkeeper Training if you can remember that. Back then it was also saving us a lot of time and effort with training and your suggestion does the same.

It's also why I deleted the idea to train 11 (or like you even 13) players at one time. It is too much time consuming, I mostly do 1 or 2 players every season. Of course with your strategy you have a lot more potential.