Tom can not be kept on the bench. His is unquestionably one of the top 5 (3). For my money I try to get a 2nd for Bak and start Yosh at LT, Tom at RT. Its a downgrade, but if Yosh doesn't take that final step you have draft capital to get your LT of the future instead of desperately trying to rework Bak's deal in the offseason. You also get younger either way.
I also don't want to piss off a young guy who has earned a starting spot. Not unless you have had some real serious conversations with him and you are positive he sees the big picture.