For assessment of the GC, I think we would want to orient around the performance of the GC, and ideally quality over quantity. And so I think the measurement will need to be qualitative(overall review of the work) over quantitative (kpis).
As a result, I would prefer a forum post with a summary of aims and accomplishments for the season, with a poll for review of that work, and based on that unlocking tiers of bonus. (Still chewing on this…)
Ultimately, (and in my opinion) the measurement of the GC is a mix of all the metrics above(and more), which reflect a GC that is attempting to further the mission of the DAO and support a healthy project ecosystem. (Which I think the current GC has done a GREAT job at! 
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