The idea of a permanent fix sounds good. I am not sure how it is going to work, I wonder if they have tried it in an animal model already?
Apart from the method of getting the gene therapy into the pancreas which has to have a few percent chance of causing pancreatitis, as pancreases get inflamed if you look at them let alone infuse anything into them.
And it has to be the real GLP-1, or something very similar , which has a very short half life, and to have effects anything like the drugs it would have to make a lot of it, as glp-1 agonists tend to be given at levels orders of magnitude higher than endogenous GLP-1, and you would not want to get too many copies of the gene working or you would get side effects that never go away.
And then there is the cost, the few gene therapies that are actually used cost millions.