Vascularized Pancreatic Islet Capsules?

Efforts to ameliorate or cure type 1 diabetes by transplanting either the entire pancreas or the functional units of the pancreas, the beta cell islets, have had little success due to their destruction either by normal immunity or by the same autoimmune response in the patient which caused diabetes in the first place. Also, with about 800,000 type 1 diabetics in the U.S. and only about 5000 cadavers becoming available for organ harvesting each year, the donor supply could never make any difference in the disease epidemiologically.

A major alternative to this approach has been to transplant animal pancreas islets encasuled in a differentially permeable membrane which allows insulin to escape but which blocks the entrance of immunologically active cells. However, a decisive problem with this alternative is that the islets within the capsule rapidly decline in function and die because they are not revascularized by the host's body from outside the capsule.

My question is: Would it be possible in principle to permit the host's body to revascularize the islets within the capsule, or would that disrupt the encapsulation barrier too severely or destroy the islets through vascular-based immunity? Any advice would be appreciated.