Individual Player Substitution Not Available

In Open Practice mode you can substitute individual players in specific formations (by pressing triangle in formation selection). However, the substitution function is not available in Practice within Dynasty Mode. Why? Seems like this would be a simple addition. The problem is that I cannot select the players that I want to play in certain formations and am living with whatever the computer throws out there. 

in game subs are too difficult, because you can only do this when the play clock is running. And I don’t want to have to run through the same substitution changes every game. 

side note. Changes made in practice mode do not save. Why isn’t there an option to save progress anywhere?