Can I Have a Reverse Tummy Tuck After a Whipple Surgery & C-section? I Have Been Warned About Blood Flow Due to Scar Tissue.

An examination would be necessary to determine if your existing surgical scar would be suitable for a reverse abdominoplasty.   I do not think you would get as good of a result as a standard abdominoplasty but your scar would place your at an increased risk for tissue ischemia.  

The reverse tummy tuck is not done very often.  Besides placing the scar in a more visible location, it seems the blood supply to the remaining skin may not be as good. The scar is not an issue with you since you already have one. If your C-section scar goes horizontally, I would probably not do it, since that would block the circulation from below. If it goes vertically, then it might be doable, but conservatism is the key. Your main problem seems to be with the diastasis, so the undermining of the skin could be more restricted, just enough to repair the diastasis without having puckering.  All of this obviously would need to be discussed with your plastic surgeon.  good luck