What I stated is actually Mario’s philosophy. He cross trains his OL and puts the best 5 on the field. This is why Rivers wound up at LT to begin with. It's not his best position, but he is good at it, which allowed Cohen and to play at LG and Cooper at RG.
It could change next year with either Bell, Pancake, or McCoy as the starter at LT. Personally I think Pancake will need another year because of injury. Hopefully he gets healthy and can contribute next year.
Everyone will get better. The younger players will make the biggest leap forward. We'll see how it plays out. We have good problems with the OL room.