There is no procedure for a beta cell transplant currently, so the fact it doesn't exist probably constitutes a problem.
There is an islet cell transplant. So a pancreas is mashed up and islet cells are extracted (the extraction process doesn't get so fine as to extract beta cells only), the islet cells are given to the recipient by being injected into the liver. There is a risk in the the procedure itself of causing liver damage/severe haemorrhage in the liver. You need a healthy liver to start with and as the islet cells set up and start working in the liver there can be an impact on liver function.
One islet cell transplant isn't sufficient to create any real reduction in exogenous insulin requirements, or to reestablush alpha cell function (which is the other thing islet cell transplant does) so 2 or three islet cell transplants are recommended. The recipient should get a second islet cell transplant fairly soon after the first, ideally within 3-6 month. So that means you quite quickly want another matched donor to die for the first transplant to have been worthwhile. So that's quite an awkward place to be as the donor recipient.
They won't do more than three islet cell transplants to preserve liver function.
Islet cell transplants aren't judged as being successful when they cause exogenous insulin requirements to cease. There is a much lower bar for islet cell transplant success, that's judged by a 25% reduction in insulin requirements. Any reduction in insulin requirements is not expected to last long term - a five to ten year lifespan only.
So whether you consider only achieving a second honeymoon period as the benefit of a transplant procedure might be seen as a problem.
While the islet cell transplant is working the recipient would have to take immunosuperessants, these carry risks of kidney damage and skin cancer. But they do not block the autoimmune desire to kill of beta cells which caused type 1 in the first place, hence the short lifespan for an islet cell transplant.
So risks from the immunosuperessants would also be considered a problem.
