If 1 member from each vampire blood line came together and bite 1 person at the same time. Not enough to drain tons of blood, but just enough to transfer the virus. If the person did survive would they be more powerful and have all the attributes of each vampire, or would they be a deformed monster.

Molag Bal would come down from Coldharbour and [censored] the new vampire until he or she died because it's such an abomination. Then Clavicus Vile would try to make a deal with the dead corpse which would make Meridia mad, starting a full blown out war between Daedric princes, destroying Tamriel in the process.

I think Molag Bal would make him/her his new Champion.

Would all forms of the virus take, or just the first one?

This is a purely hypothetical response, but I figure whichever strain is most dominant. I say that as in whichever one infects the most cells the fastest, because eventually the strains would need to fight. The strongest strain would be the one to take control.