it is a good idea and in my oppinion should include all data available concerning the cheaters (username, social accounts, MEW account, etc)
This will not stop these parasites, but will give them a lot of additional trouble, maybe cheating can be turned into something not worth
I think it should be public in name of transparency and to avoid misunderstandings (imagine you unfairly input someone on the list, he should be able to defend himself if he wants)
Who will be able to edit the sheet? it needs to be more than one person, but restricted to a few...