So, I love vamp, and my favorite clans are (by a wide margin) the Giovanni & Cappodocians. Spooky undead necromancers just sits right with me. Perhaps its the Warhammer Fantasy of my youth bleeding through.
In VtM, the Pisanob, and their leader Pochtli, are somewhat oddities for the Giovanni. Apparently, the Giovanni traveled to central America, and found a family of necromancers there, practicing essentially the same nigrimancy as they did, whom they promptly embraced into the family. These are the Pisanob, one of the minor branches of the Giovanni, locked in a war with the Harbingers of Skulls and the Sabbat.
Pochtli himself is supposedly a premescine (a member of the clan from before Augustus put the bite on Cappodocius), but it's unclear if that means he was an existing cappodocian, or one of Augustus's childer. Considering his central american appearance, name, customs and so on, it seems unlikely that he's one of the standard Giovanni.
(everything after this point is stuff I'm making up, based on my own fan-theories)
So, here are the assumptions for this bloodline. There are, actually, two bloodlines that make up the Pisanob. One is the main Pisanob. Their mortal families are native americans, and their vampiric blood comes from the Giovanni who brought them into the clan. The other is Pochtli's Children. These are again descended from native american mortals, but their vampiric blood comes from Pochtli. Pochtli himself is a Cappodician Elder who (like The Capuchin and Baron Samedi) has managed to come to some agreement with the Giovanni. Unlike Samedi, though, he's managed to have his childer absorbed into the greater Giovanni clan.
The bloodline is largely indistinguishable from the greater Pisanob family, forming the inner circle around Pochtli and the rest of the family's leadership. Nominally loyal to the Giovanni, they in fact hold that Gehenna has arrived, and that Augustus is not strong enough to defend his childer from the other Antediluvian when they rise. Instead, they are bolstering their own defences so that when the time comes, they at least stand a chance of surviving.
Pochtli's Children tend to focus rigorously on necromancy, often neglecting other disciplines entirely. Many have strongly intellectual concepts, focusing on mental attributes and knowledges, but a good proportion are physical-oriented, combining necromantic power with combat ability in their wars against the Sabbat.
Bloodline Disciplines: Necromancy, Potence, Auspex
My reasoning is that this puts them firmly between the Giovanni (necromancy, potence, dominate) and the Cappodocians (necromancy, resilience, auspex). Potence fits the 'spooky monster' archetype in VtM (hence why the nos and the lasombra get it), whilst Auspex tends to be found in more cerebral clans.
Bloodline Weakness: Pochtli's Children gain half the benefit from blood taken from living donors. If the donor is dead when they start drinking, they get the full benefit. Furthermore, they can't ever spend blood on the Blush of Life; they will always look at best unhealthy and at worst corpse-like.
This works out similarly to the Giovanni weakness when the vampire feeds on living hosts, since they deal two damage for every point of blood they get. The difference is that Pochtli's children feed on living hosts less efficiently, so while a ruthless Giovanni can get 10 blood from a mortal, Pochtli's children only get 5. This pushes them to mess around with corpses, or at least kill their victims before they feed. The 'no Blush of Life' thing is another throwback to the Cappodocians, putting them somewhere between the two clans.