As it is, what your suggesting will never be changed. It's in place so that BB users stress depth instead of simply loading up on high priced star players and then playing them to death every game. We all understand that it's not realistic to sit star players but it brings a lot more strategy into the game and forces owners to build deeper rosters.
As it is, 80-85 minutes isn't the kiss of death, you might find that some of your players maintain or even improve their gameshape in that range. But if you go over 90-95 minutes I think that you'll almost certainly see them fall next week. And you can train gameshape this week if you so choose.