I think Barnaby hit this pretty solidly on the nail.
You can have grades of experience in your company, and in fact may not be able to get away from it given how HR often stratifies job titles. However, what you need to make clear to everyone is that it is the team that is measured on the collective success or failure of the team. There are no rockstars in the team, just teachers and students which can be interchangeable depending on the skill (Bob is an awesome C++ coder and teaches Sally. Sally is a goddess at Java Script and teaches Bob).
If you are a rock star coder, and your team is struggling to perform, you don't get a new team. Instead you get asked, "what are you doing to help the team get better?" I'll take a team of average coders who are really good together over a couple of individualistic rockstar coders pretty much any day.
There is a newer HR assessment model that really supports this. Instead of an individual being reviewed on their personal success, the model is split 50/50 between team and individual development. The first 50% of your review is based on the success of the team. If the team score is 100%, you get 50 points. If the team scored a 50%, you get 25 points.
The second half is based solely on individual development based on goals set by the employee and manager. Did you learn that new language you signed up for? Then you get a high development score.
The key is the individual isn't measured for work done, the team is.