Hi Paul,

Yes it is doable. Having been on opioids as long as you have, there are a couple phenomena that may be helpful to know about, ask your doctor, and/or look into yourself.

When some people rotate opioids, especially after a lengthy period, they may find that a lower "equivalent dose" will provide the same analgesia as their previous medication.

Long term intractable pain, as well as opioid therapy, may deplete/suppress adrenal hormones, which can result in reduced analgesia - patients feel like their medication isn't working (as well) anymore. Testing for this is just a blood test, and these hormones can be replaced/supplemented, which can reduce the perception of pain, help the medications work better (requiring less), and improve overall feeling of well-being. See:
http://neurotalk.psychcentral.com/thread156416.html

Also, as you mention weight loss, there is also a diet specifically for chronic pain patients. I've been on it for over a year now, and it's the only diet I've tried (out of many) that has helped me lose and maintain with reduced activity due to intractable pain. You can find the diet here:
http://pain-topics.org/pdf/IntractablePainSurvival.pdf
(Page 34, but the whole free book is excellent and indispensable)

HTH,

Doc