I think we should have they choice of draining the dead of their blood for vampirism. The point is because i have fast traveled into the cities without realizing that i would be turned into a full fledged vampire and then people would attack me. If we were to kill certain NPC's for their blood in a bottle, then we could safely fast travel into a city without being attacked.
Its not uncommon in Vampire genres that they are required to live off the blood the living only. The answer really is NOT to fast travel into a city if your at stage 3. Go to the nearby stables first. (which can also offer an opportunity to feed on the sleeping stable master).
Just saying, it was useful in Oblivion to have those things, and it sounds logical that a traveling, vampiric hero would carry one.
I don't recall bottled blood in Oblvion.