Adaptability in immune system
No. MHC works differently from any other antigen. MHC is involved in the maturation of T lymphocytes in the thymus. Forming lymphocytes need to recognise the MHC with a certain affinity (lymphocytes with too much affinity for the MHC are destroyed). In all this process there is no intervention of foreign antigens, so the system you propose won't work because the lymphocytes would search the MHC of the graft and they would attach them with abnormal affinity. This would trigger autoimmune response.

What you propose is the main functioning of allergy vaccines. You expose the immune system to low dose of antigen during long time, and that would make the body to not react aggressively to the substance. However, this phenomenon is based in B lymphocytes, which recognaise soluble antigens and little cells (humoral immune system) instead of whole cells (cellular immunity).

In the domains of science fiction, however, it would be technically possible to transfect thymal cells in order to express the MHC of the donor, since it would express both. Actually, this should be theoretically easy (The thymal cells seems to express almost any protein in the body, in order to prevent autoimmunity), but it face the problem of thymal degeneration.