Javier, a 28 in N mount will never happen. If you can accept manual focus Contax, strongly consider the Aria + 50/1.4 + 28/2.8 - my favorite kit. For Contax AF, there is the RF G1/G2 + 45/2 + 28/2.8 option.
Not exactly your desire, but fine systems both.
Not exactly your desire, but fine systems both.