I'm all for starting the best player at LT. If Monroe walks into training camp with a good attitude, and performs better than Stanley start him. Let Stanley sit back and watch the game, make sure he is studying, and if Monroe gets injured we'll have a player ready.
I don't think Stanley will be able to dethrone Wagner at RT. Wagner had a Serious foot injury late in 2014, before the injury he was a top 10 tackle. He wasn't playing at 100% last year. I expect him to play at a much higher level now that he has had time to recover. I would rather find another capable starter at G, and let Stanley focus on Tackle in case an injury were to happen, and start him next year when Monroe is packing.