Against - It would be a huge waste of development time and resources to implement this imo.
Group performance depends on team-work and good team-work means you don't always do what is optimal for you as an individual but what will be best for the team. A system like this would discourage team-work. People would not do what was best for the team if it was detrimental to them as an individual and might possibly reduce their reward.

Playing a game should be fun, and doing it well really is enough reward for a lot of people. I don't think there is anything to be gained by adding a whole new system to measure and reward performance just to cater to those who won't do their best unless given added incentives.