This is not really a new idea, but I don't think it made it in the migration from the old feature requests. The idea is to beef up Peer Evaluation to make it more useful in the context of a group assignment. There are several elements to this, and I have been asked to submit each one separately, so here goes. To see the other ideas, try searching on Peer Evaluation for Groups.
When assigning a Peer Evaluation of a product (that is, whatever the group submitted), students should only ever be assigned to products other than the one their own group submits.