Karin and Sasuke/Neji or Hinata/Hanabi and Naruto.
I think that these are the only real combinations that matter. The main thing is that the Uzumakis bring their special chakra to the mix and Sasuke/the Hyugas bring their respective Kekkei Genkei. This is essentially merging the two bloodlines of the So6P back into one person. I am still under the impression that the Byakugan can evolve in some way, since the Hyuga and Uchiha are related and at one point in the series the Byakugan was said to surpass the Sharingan in its level of perception. Additionally, Ao (with a transplanted Byakugan) fought against Shisui (considered one of the best Sharingan users), and even though we do not know any details of the battle, somehow he managed to survive. This is an indication that if used properly, the Byakugan can at least match the Sharingan in combat. As of now, though, I think an Uzumaki with the Sharingan would be better than one with the Byakugan, which would have me lean more towards Karin and Sasuke over one of the other possibilities.
