Why is BMI important? Because the higher the BMI, the greater the risk. Time after time I read comments of women seeking a plastic surgeon who accepts high BMI. Standards set by surgeons in the US will not allow a procedure if your BMI is over 30. In the DR, I've seen surgeons accept as high as 36. However, many are realizing the risk and reducing it to 34. For standards in Colombia, I've seen 32 as the maximum BMI level. Research has shown risk factors for heart attack, wound infection, and urinary tract infections are greater when the BMI is higher to name a few.
A snatched waist isn't the only part of your body you should want to look slim or small. The "linebacker" look is real and not appealing. I recommend getting down to a stable weight that you know you can maintain.
It's ok to postpone your plastic surgery and seek bariatric surgery (weightloss surgery) first. It will make your final results look that much better, not to mention health wise you'll feel that much better.