---> "strictly follow depth chart"
Except that is still strongly stamina based -- if you have two roughly equivalent players, and the starter has very high stamina, he can play in the mid-40s in minutes, while if very low it can be in the low 30s.
I think a better option would be, for each position, to have an option for how you want substitution handled:
-> Keep Them in!
-> Rotate them!
-> Play to win!
So if you're trying to get near or to 48 minutes, you'd use the first; if you have roughly equal players you could use the second and get balanced minutes, and the third would let the coach pick whichever player is best at a given time.