2. Nero
Ok, I take it that this is unlikely due to two major reasons. But hear me out. Firstly, let's address Eric Bana. Sure it's quite unlikely that he would agree to appear on a regular basis on a Star Trek television show. But that's not what I'm suggesting here. I'm suggesting that Nero is the antagonist for the very first episode (a traditional two parter of course) of the new series. He might sign on for such a significant role, especially seeing as we can expect that at least the pilot will get decent ratings. Also if the production was very accommodating to his availability increases the very low likelihood that Bana would appear in the series. But we can hope. As for Nero himself, it would actually be fairly straight forward to explain how he arrives. He arrived in the movie universe by going through a blackhole created by red matter, which also threw him into the past. So a blackhole created by red matter in the movie universe potentially could lead back to the prime universe. Of course the Nerada went back in a much less intact state than it did the first time, but characters in film and TV have survived worse. So Nero would be left back in the prime universe without a ship (although considering the Nerada was converted with Borg technology then who knows what sort of level of regenerative abilities it has) and plotting his revenge especially as in the prime universe, Vulcan is still intact.