Spiky, I think that was a great summary of some of the long term concerns. I'm a couple years younger than the OP and your daughter (36) and have thought many of the same things. I don't know if I would have gotten heavier, but I do know that I would stay obese, even if I lost and kept off significant weight. I also know that most likely I would be diagnosed with type 2 diabetes, probably within the next couple of years, based on my blood sugar trends. I suspect, looking at the disease progression in my grandfather, father, and brother, that by the time I would have been 45 I would start to develop diabetic neuropathy no matter how well controlled my sugars are, and by 60 the neuropathy at best would include significant pain (my father, who is very active, eats low carb) or limb loss (my grandfather, who was sendentary and alcoholic). I was on 3 blood pressure medications, so I also have a good chance of suffering slow organ damage, and more recently my lipids are going up, making heart problems and strokes a possibility.
So, I could have waited, as I am still pretty healthy. But in 10 years? In 20? I had assumed a shorter life span. Duodenal switch offered me the possibility of a more normal one, or at least a higher quality of life. I could wait until I started to get sick and then have the surgery, but prevention of disease progression makes more sense than trying to treat it later.
I have thought about the real possibility that within my life span we will have much better options. I sure as hell hope so, for the DS certainly isn't a good response to the obesity epidemic. I do believe, though, something as effective as the DS will take a while to be offered, and new treatments are risky. Even if I knew in 15 years a super probiotic as effective as the DS would be available, the decision would be much harder. However, thinking like this is such a gamble. You could have thought the same thing in 1990. The only new options are the sleeve and some meds, and we know how ineffective these can be compared to the DS.
Maybe the DS will have deleterious effects long term. I think it has been around long enough that at least most of the time the negative effects aren't as bad as the effects of morbid obesity. At worse there is always surgical revision (*shudder*) and/or enzymes to increase absorption.