I don't know if much has happened with the research since, but the theory was since only beta cells are targeted by the autoimmune response, perhaps these "pseudo Beta cells" might be left to produce insulin without being attacked. Does mean you're potentially left with inhibited glucagon production though. Perhaps gene therapy altered alpha cells could be implanted rather than altering the ones you have.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5757249/
I don't know if much has happened with the research since, but the theory was since only beta cells are targeted by the autoimmune response, perhaps these "pseudo Beta cells" might be left to produce insulin without being attacked. Does mean you're potentially left with inhibited glucagon production though. Perhaps gene therapy altered alpha cells could be implanted rather than altering the ones you have.