Modernist Cuisine-style BBQ brisket safety
I am not aware of any rigorous tests done on a sequence like you propose.  In the absence of data, I simply assume holding any open cooked product more than a week in the refrigerator is risky, smoke notwithstanding.  

You can significantly boost your safety by soaking your brisket for at least 24 hours in an acidic salt bath -- perhaps with some brown sugar and aromatics for added flavor.  Consider, for example, a recipe like Alton Brown's corned beef, which IMHO is tasty.  (Add a dry rub of fresh-ground black pepper and, say, a little fresh-ground allspice and juniper, and you have pastrami.)

By the way, after smoking you don't have to wait for your brisket to cool: any vacuum bag suitable for immersion/sous-vide cooking can easily handle a brisket right off a 150*F smoker, no cooling/waiting needed.  Besides, if you submerge the still-hot brisket after sealing in its bag into a 150-160*F water bath for 10 minutes, you will have effectively Pasteurized your product; with the residual salt and acid, I personally would be comfortable holding the sealed bag in the refrigerator up to two weeks (if I needed longer I would freeze it).