User blog comment:Raababukk/Possible New Power ups for Issei Hyoudou/@comment-24098614-20131230091831/@comment-1359322-20131230152547

That's why Rias and Akeno is still scattering his Dragon powers. They literally know nothing about Issei's new body. Issei himself doesn't even know much about his new body. Any power-up based on Issei's body probably won't be done unless they can know more about it, they can't risk having Issei die while trying to become stronger after all.