How could Type A, B or AB blood be biochemically modified to not elicit an immune response?

Firstly, the blood cannot be modified, but it can be controlled by means of immunosuppressive treatments.

Explanation:

The treatments that are usually used are immunosuppressive treatments, where the efficiency of the immune response is lowered, the most used is the treatment with corticosteroids, and this happens because at some point the rejection of different blood phenotypes is not the fault of the blood or cause of blood that is why you cannot change the blood factor.

The cause of blood rejection and systemic failure if we mix two factors of different factors is immunological rejection through the histocompatibility complex, which this phenomenon is a surface recognition protein for red blood cells, thus generating a recognition of the proper and the non-proper, if we inject or inoculate blood from another factor, a person will take it as not their own and the immune response will destroy it, generating hemolysis, and systemic failure, therefore death.

All this response generated by the immune system against the unknown is regulated, controlled and decreased through immunosuppressive treatments such as taking corticosteroids.