I'm a HUGE proponent of people starting their own businesses. I got in to brewing hoping to one day expand it in to a brewpub.
Yes, restaurant experience would be nice...
Yes, all-grain brewing experience would be nice...
Yes, business experience would be nice...
Personally, I believe that where you lack in some areas, you make up with by aligning yourself with the right people, and delegating the work appropriately. I don't have any restaurant experience, but if and when I do open up my establishment, you better believe I'm going to be talking to some very experienced restaurateurs.
This is not an impossible venture AT ALL. It will be a life-changing venture for sure. It will be a very difficult and frustrating venture. The restaurant business is a vicious beast, but people do succeed, and there is no reason your friend couldn't.
P.S. I read Brewing Up a Business by Sam Calagione. I won't say it is the end all be all of reference books to opening up a business, but it does discuss a lot of the things he had to do when opening Dogfish Head. I'd suggest you check it out.
http://www.amazon.com/Brewing-Up-Business-Adventures-Entrepreneurship/dp/0471708682