I guess I look at it that these guys have been playing most of their lives. They are well aware of the physical nature, and know as they move up the ladder it gets more physical. Trying to protect them from not getting hurt, in my opinion, makes no sense. Injuries are part of this game, and you just hope they don't get hurt real bad. Whether you protect them or not, they still may get a season or career ending injury, you just hope it doesn't happen. I don't think there is anything that can be done that won't affect the players regular game.
Over the years these guys have been playing, learning to hit is just as important to a bigger more physical player as learning to not get hit is for a smaller less physical player. Going to games the last few years, and seeing the play in the corners in front of me, I am always amazed at how little these guys move to avoid getting slammed into the boards. Sometimes, it is just a matter of changing the angle of their bodies that turn a solid hit into a glancing hit, or a total whiff.
Bottom line for me is to let these guys play their game, if they look like they can move up, then move them up. Playing against tougher talent is how they improve.