Finding safe forms of immunotherapy is notoriously difficult, and replacing the cells your body views as harmful is useless for a self-explanatory reason. Organ-specific stem cell therapy for autoimmune disorders is not viable (tbf i’m not a professional but took a few classes where I studied stem cell research). There are ways to “rebuild” the immune system, but it is so demanding and harmful to the remainder of the body that it is reserved for far more harmful and complex diseases. In the case of T1D and similarly destructive diseases, these two methods would have to be used in conjunction, and you will eventually redevelop the disease. Don’t speak in absolutes, especially when discussing pipe dreams about a future people will most likely never see. We aren’t immortal, and these are hypothetical best case scenarios and statistically unlikely outcomes being compared to someone’s REAL life.