I'm aware that this will prob not be a popular stance on the forums and that this subject has been beaten to death over the past few months, but i believe that the new Orc Allied Race should be from AU Draenor and not Outland. I know a lot of people want to forget about WOD, but it happened and i think that forgetting about it would be a waste. The advantages of Draenor Orcs over Mag'har would be that it opens up the other clan skin colours (Blackrock, Shattered Hand, Bleeding Hollow, etc) and that it would level out Alliance/Horde power, as imo the Horde seems to be weaker then the Alliance and has never recovered from MOP.
If WOD characters are brought back, i think it should be ones that have not been mentioned in the MU, so no Draka, Durotan, Rulkan, etc. With the only exception being Grom. This is for three reasons 1, Hes my favorite warcraft character and i'm biased and 2, Now that Draenor is at peace, Having Grom and other loyal followers there would be awkward, so exiling them to Azeroth would make sense. Grom would join the Horde as it would give him a chance to redeem himself for all the needless Iron Horde Orcs he led to their deaths. I think it would also be interesting to see a young Grom try to live up to the standards MU Grom set in the horde. 3, To me the orcs represent the noble savage archetype and with Saurfang being the noble, we need the savage and love him or hate him but Garrosh's absence has left a huge hole in the Horde that needs to be filled and who better to fill it then Grom.