Wet House?

I have not heard of the idea of a wet house so I don't feel educated enough about the concept to judge whether such an arrangement will work for what you described as a tragic situation for you, your brother and your family. Without constant monitoring, I am not confident that an alcoholic in your brother's circumstances - with substantial brain/cognitive damage and liver damage - will be able to live in a secure safe environment successfully while feeding his addiction.  I wonder whether a first step might be to get your brother detoxed and then explore an appropriate setting (inpatient rehab, hospitalization) to deal with his mental and physical condition.  Supplying alcohol to your brother in a controlled setting - a guest cottage - would not be addressing the substantial underlying issues of his alcoholism, nor his liver disease and psychiatric impairment.