Different antigen detection triggers an immune system response that could perhaps stimulate mitochondria and such in killing cancer cells - something like chemo without the hair-loss?
No. When a different blood type is introduced in the body, the host immune system recognizes the foreign blood as non-self and attacks it. The transfused blood becomes useless, and the potentially massive immune reaction can cause shock, which itself can be fatal.
More details in the book Blood Groups and Red Cell Antigens, which can be found at the NCBI library.