I believe that key components are visibility, accountability and peer review., i.e. very much reputation.

Here may be a way to roll this ball - I have not tried it myself, but it might work. 

If you make it known that all groups should evaluate themselves and that this evaluation will affect their grades. Perhaps it best goes in as a plus factor rather than an requirement. 

Do it such that

• I get to grade me and my input to the task
• The other participants grade me in exactly the same manner
• The group then grades the group
• One of the grading questions is - Rate the honesty on your statements

As someone stated - any system defined will be gamed. Therefore, to keep them honest, do not show the form in advance and modify the evaluation question from one year to the next even if the gist stays constant.. 

A good book to read is Hugh Grant's Give & Take - there are research based findings that he present in there. The gem in his book is the reciprocity ring which the above mentioned thoughts are based upon. 

https://www.amazon.co.uk/Give-Take-Revolutionary-Approach-Success-ebook/dp/B00CAUH7UE/ref=sr_1_1?ie=UTF8&qid=1503320446&sr=8-1&keywords=give+and+take

Good to weigh in the rating may be also the 12 rules as outlined by Marcus Buckingham in his book First break all the rules (slide #3), where (being the father of teenagers) I find that points 1 & 2 matter the most. 

https://www.slideshare.net/alexgrech/first-break-all-the-rules-1481256/3-12_Questions_1_Do_I

An obvious question for each individual would be 

• Did you get to do something you feel you are doing best?

One or two checkpoints along the project path might help stragglers understand what is going on?

Your job is then reduced to making check on factual knowledge of the topic etc. This is most easily accomplished by stating a few open ended questions on the simplest of things, i.e. questions that can have any answer but only one answer if you actualy have done the things you state you have done. Another way is to ask Student A something to explain to Student B. 

From personal experience - I once held a completely new course. It did not have a precedent. Students acted in a (better) way I have neither seen before nor after. The difference had nothing to do with teaching skills, student mix. The courses that ensued were very much the regular run of the mill.

My observation - it all boiled down to the students not knowing exactly where the bar for exam was set.  This forced them to actually having to understand the course contents, rather than learning how to respond to the course material. Simple as that. 

Just my 2 cents. 

Hope this helps

Claes

In my opinion, it would be interesting to make the task allocation based on the learning style of each learner, they may be pugnacious and show more interest to the task and subtasks assigned to them. you may read about the theory of Kolb team learning experience.

I think considering learners’ social features: their capabilities, learning styles and preferences, and the objective conditions of the assignments or other assessments they are facing, would support them to be more focused on teamwork.