Just seeing that TI has convened a group to make recommendations for the UNCAC monitoring and enforcement:
The Council of Euorpe's GRECO system seems like a good example to follow, but the UNCAC system has so many more countries included with so many different levels of corruption, that it would need to be tiered so that you didn't have very corrupt countries peer reviewing countries with very low rates of corruption. But how do you do that without stigmatizing countries in what would be the lowest tier? And how would you create a system to categorize those who are monitoring? Big headache.
I feel like it's the same problem as the human rights committee at the UN, where abusers sit at the same table as those who admirably protect human rights. But creating some big monitoring agency doesn't seem like a very good idea either; they become another actor in the whole process accused of being biased.