Funny, another forum I post on had a link to smokerless brisket recently and your post reminded me
http://www.chefsteps.com/activities/smo ... ed-brisket. They use a cure to mimic the smoke ring ... unrelated I know, I digress ...
Generally ribs don't need a brine to tenderize them. With that said, I have heard of people rubbing a cure on ribs a few hours before smoking to get a deeper smoke ring then rinsing it off. I personally think there is no need but to each their own I guess.
Three things you could try if you really want tender ribs (I myself think there should be a little toothiness and they should not just fall off the bone) The first trick is to remove the thin membrane that runs along the bone side of the ribs ... just slide a knife underneath and loosen it at one edge thenm using some paper kitchen towel for grip, grab the membrane and peel it clean along the length of the rack. You should be able to remove it in one long shot. This membrane creates a tougher bite as it shrinks and tightens during cooking.
Second, smoke them according to the 3-2-1 rule (I actually prefer 3-1-1 but the 3-2-1 method will bring more fall off the bone type ribs). Rub with a spice rub, smoke for 3 hours uncovered, wrap in heavy duty foil tightly with some honey, brown sugar, splash of beer, favourite bbq sauce, apple juice, whatever you like to use (experiment, I like a light coating of brown sugar, equal amount of honey, and a splash of a good dark beer) Make sure it is wrapped tightly and return to the smoker covered in foil for 2 hours (or in my preferred method just 1 hour) After that is done remove from foil and place back in smoker uncovered to glaze for the last 1 hour (hence 3-2-1) You can brush on ths reserved liquid from the foil or some BBQ sauce too.
Last, if all else fails and you still want them even more tender do one of two things ... use some meat tenderizer powder in your rub (this is derived from pineapple) or add some pineapple juice in with the foil in step two of the method above. Pineapple naturally denatures protein and softens meat ... however too much and it turns to mush so don't marinate it for any prolonged amount of time.
Hope these suggestions help! Let me know if you want any more help or clarification of anything above! Good luck and post pics of your cook!