Cooking ribs weirdly?
There is no problem with the brine, smoke, sous vide process as long as he pays attention to typical/safe temperatures. I would sous vide then smoke and probably return to a hot grill, rather than sear, but that is personal preference. What would be unusual would be a return to the brine after the smoking.  While it could be made safe from a food-safety standpoint (new brine...well-chilled...), I don't think that would be desirable or all that beneficial. Have him take a look here for detailed tips: https://www.chefsteps.com/classes/barbecue/#/dry-style-baby-back-ribs