I've not used a BOP but there is one in Alexandria VA (I forget the name and worse a quick google fails to find it!). Anyhow, it was also a micro brewery/brewpub along with BOP.
There is some sense to trying to make it a 2 or 3 focus location instead of just one - ie LHBS +BOP, but this also means you get all the downsides. Some of these thing vary by state. In VA, there is a sperate liscencing for being a LHBS and a BOP and a Brewery (last time I look at this sort of idea). You might be appealing to widely different customer bases. In terms of the BOP, doing extract makes the most sense, because kettle time (one of the things being sold) is longer for AG brewing. In a large portion of the store will be taken up by warehousing fermentors. Which goes to rent of the space. What to do if a beer goes unclaimed, etc.
I was in contact with one of the distributers, and they had a number of the population who homebrewed, and who make wine at home (why be choosy? as a business person your product is little green peices of paper, not beer or wine) Anyhow their back of the envelope numbers were you needed an area population of about 200K with little to no competion for a LHBS to make it and then it would only be about breaking even. Granted this was based on the numbers of people on average who brew or vint at home, and that number may have changed. It also was based on an average amount spent per person (I think $100).
And now I should delete this rather than post since I'm not sure I've addressed the OP's question, but just rambled.
I think a BOP can be done, but it is hard. In the US, Beer is something we buy, or make at home. There isn't a great amount of us who make it outside the house. Same with those kitchens you see where you go there and cook 10 or meals and bring them all home.