Well I think there should be some stamina rating, in other words if you're playing that many guys all game their performance shouldn't be as good based on natural athleticism, age, and minutes over the season. However the length they got to is just ridiculous in comparison to real life, a guy can lose GS while playing 30 minutes a game depending on how many are scheduled.
How about they fix the problem you mentioned above with a chemistry rating(much more like real basketball and no included enough in sims), where a team that has been together longer will play better(although once they hit a max point it will make no difference). Part the reason I like sims like drive the lane(now down, but hopefully coming back) is that you get a decent understanding of your players, but you don't know for sure what lineup will work the best, their stamina, hidden ratings, etc.. It manages to be simple but with enough complexity to be challenging.