There's other questions that need to be answered first.
Do you qualify for bypass surgery based upon your BMI? Are you considered morbidly obese medically? Do you have other medical problems? Will your insurance company cover it, or will you have to put up a good fight (doctor's documentation, years of medical comorbidities due to excess weight, compromised medical history due to obesity, etc.)? What type of bypass are you looking into? Are you a high risk patient?
To qualify for a tummy tuck/lipo/full body lift post gastric bypass with a credible surgeon, you will have to maintain your IDEAL weight (which most patients NEVER reach, although many have a healthy BMI temporarily) for an extended period of time (varies from surgeon to surgeon). This will also probably not be covered by insurance. Pricey surgery (surgeries) so be prepared.
I understand your frustration with the excess skin. I have never had a tummy tuck, but one part of my profession is working with individuals attempting to qualify for gastric bypass as well as post op patients (medically as well as mentally).
I hope this post helps you and I look forward to your reply.