cherrybim- this has actually happened already. You may know that there is a remarkable DNA study done on Kohanim that shows that over 80 % share a similar DNA -unlike other jews, poiting to a common ancestor (Yes, I know that there is a tribe of black africans who sahre the same….) Also, it is pretty clear that most jews share common DNA and that DNA studies today can identify common ancestors of long ago. so, indeed, bodies are different, even if only very subtly.
as for medical cures, i think that most doctors would acknowledge that different ehtnic groups react differently to different medicines.
As far as a Beth Din, I can’t tell you but I suscribe to the halachic custom to incorporate modern medical knowledge in our psak also…hence, the argument about when is the time of death..etc.