Hmm. I was thinking about this when I went to lunch here in Tucson...
There are really two approaches I would consider: the one I mentioned and another, similar to the 3-2-1 pork rib method. The problem is that it is hard to predict timing on the latter approach. With your time limitations you could really only smoke for maybe 90 min tops and then you'd need to foil (with a little liquid). You could, however, increase cook temps at this point to, say, 325/350 (grate/lid). Without seeing the thickness of the ribs it is hard to say what the timing should be but it is quite possible to simply wing it at this point and foil for, say, 1 hour before checking them. At that point you'd probe them to get a feel for tender. You would not need them to be completely tender at this point--just somewhat-to-fairly; i.e., tenderer. You'd go another 15-20 min in foil if they needed it. Then you'd unfoil and finish on the grate, basting with sauce if you wish, till the ribs are completely tender. (For the foil's liquid addition I'd go with low-salt chicken stock and a little acidic fruit juice, maybe 1/4 c per slab, each wrapped in foil (do not use a foil pan), probably 75-25 stock:juice. Tamarind, cranberry, sour cherry or pineapple would be my juice thoughts, or a blend.)
To smoke/braise using the former approach I'd suggest probably an hour or so of smoke time, then braising in a pan or a sizeable foil pack with lots of sliced onion, some minced garlic, 1 c white wine reduced to 1/4 c, and chicken stock (you could add a dried chile or two if you wish), at temps of 300-350, pan or pouch well sealed, till the meat becomes completely tender, adding more liquid if necessary during cooking ro keep roughly the same level as you begin with. Hard to know exactly without seeing the ribs but likely this would be ~2 hours of braising. Then you'd remove the meat from the pot to a plate, remove the veg solids, defat the liquid, and puree some of the solids into the liquid to serve as a sauce, adjusting the seasoning to taste. The meat will already have come off the bones--or will easily do so--and that is how you'd serve--meat atop a starch, say, sauce atop meat.
Am I making sense?
