Seems one of the biggest hurdles is there are two groups of orcs that are playable:
1) Green skin OG orcs
2) Mag'har Orcs
Most variant orc skins wouldn't fit in with OG orcs just because they wouldn't be green. Most other skin variants wouldn't fit with Mag'har because of the whole Mag'har meaning un-corrupted.
We all know, if Blizzard wants to do something, they will asspull and do it (Void Elves and Tauren Paladins for example).
I could see the Mag'har wanting to align all of their orc clans, or atleast be allies. The shattered hand, the dragonmaw, those red guys in Outland, all of the different "corrupted" orc clans that we have defeated in the past, take whatever remains of them, "redeem" them (however Blizzard wants to do that) and then you can play whatever Orc variant you want and it would still technically be "Mag'har".