For what it's worth, I too have been experimenting with cooking pork ribs sous vide as an alternative to using just the smoker. I've recently tried preparing the ribs two way with fairly good results.
I began by portioning the ribs into 3 bone sections, then equilibrium brining the ribs in a 2% salt/1.5% sugar solution for a couple of days. Then I massaged them with a dry rub. For the rub I followed Emeril Lagasse's formula for "Essence" but cut way down on salt since I was brining the meat. In both cases, after cooking, the ribs went into an ice bath and were then frozen until I got around to finishing them later.
The first batch I smoked for two hours using a Traeger pellet grill set to 'Smoke." The temperature in the Traeger varies between 145F and 165F at that setting. After smoking, I vacuum sealed the ribs, then placed them in the 'fridge overnight before cooking them in a 143F water bath for 48 hours. In that time the fat rendered out thus basting the ribs. For finishing I returned the ribs to a 140F water bath and applied the sauce after they came out of the bag. After cooking the ribs were very tender and flavorful, but I am unsure that I like the texture.
The second batch I vacuum sealed after applying the rub, then placed them in the 'fridge to marinate overnight. (Marinating in this way may just be a superstition on my part.) The following day - following Douglas Baldwin's advice - I placed the ribs in at 155F water bath for 24 hours. The transformation in 24 hours was surprising. Much more fat had been rendered. Squeezing the meat through the bag, it felt more firm than the slower cooked batch.
I froze most of the ribs, but I placed one 2-bone portion in the refrigerator. The next day I placed it and a frozen 4-bone portion in the Traeger. I placed a temperature probe in the refrigerated ribs so I could track the internal temperature to get an idea on the timing. With the pellet grill set to smoke it took one hour to bring the ribs from 38F to 108F and then the temperature stalled. I took them out and tasted them. They were just fine, if you like your ribs served around room temperature.
In that hour the frozen ribs thawed out enough to stick the temperature probe into the thickest part . But it only took a further 35 minutes for the internal temp to come up to that same 108F. So I took the ribs off the grill, anointed two with barbeque sauce and two with a Bourbon Glaze I made following Jason Logsdon's recipe, and took them over to the neighbors to get their opinion. (They're from the St. Louis/Memphis metroplex, so they know what real barbecue tastes like.) The neighbors pronounced the Bourbon Glazed ribs "The best we've ever had." I was flattered but not fooled.
These ribs are not like real barbeque. Something magical happens when fatty pig meat is left cooking over a smoldering wood fire for 6 - 8 hours, and cooking in a water bath is not the same. However, having said that, it sure is convenient. And a lot cleaner. Biting into a rib cooked sous vide, you get the full flavor of the pork and the spice rub, and the meat comes away from the bone cleanly. Best of all, it's not dripping with grease so you don't have to take a shower or send your shirt to the laundry after you've eaten. Sous vide ribs would be outstanding as finger food at a cocktail party. Add having small portions ready to go in the freezer means you can have ribs when you want them without all the rigmarole of preparing the meat, rubbing it with spices, or getting out the smoker each time.
So what's next? Two further experiments come to mind. The first is to begin by smoking the ribs, cooking them in a 155F water bath (I think that was the better choice), and then, when you feel like ribs, reviving them in a water bath before finishing them on a hot gas grill. The second is to revive unsmoked ribs in a water bath and then smoke them for 1 hour before service.
