yer its not bad idea.
its still very subjective though. substitutions depend on stoppages during a game. Its impossible to have a setting that says "Player X will play 35 minutes" and for him to get 35 minutes every single time. even approximately.
Also the purpose of Stamina in a game would be eliminated. and i think this is still one of the most mysterious elements of the game.
For example i have two players - One has pitiful Stamina, the other has Proficient Stamina.
The proficient guy plays low 30 minutes per game, 33, 32, etc..... Proficient? He never gets subbed. ever. 48 mins each time. This is what stamina does.
soooooooo i like the idea, im just not sure how it would apply for this game. I tihnk if they had this idea, it would removes the 'fun' element of training stamina, buying guys with good stamina, etc etc.