Dming the Bible: PCs from beyond the Prime

Introduction:
The text for this week moves us from the genealogies of chapter 5 and into the Noah narrative of chapter 6 (which we will in theory cover next week). This prologue to the flood provides us with many bizarre details that interestingly enough get skipped by those who believe in the literal truth of the text.
The Text:
Genesis 6 opens with the natural result of all those generations having other sons and daughters. The world is beginning to feel full and there are a rather lot of unnamed women running about. Characters known as the sons of God decided that they would make swell wives. Now we can't be very sure who these sons were, whether they were human beings of great renown or holiness ( both things that might have resulted in appellation of the title) or spiritual beings who were actually the children of God and some mate (some in early Israel assumed that the Canaanite goddess Asherah was God's wife). This latter belief would not have been out of place in the ANE or even out of place well into the common era. The world was full of the unexplained and mysterious; it seemed a reasonable bet that the world in which we lived was full of supernatural agents who influenced the world and our lives in ways beyond our control. The gods of all the surrounding cultures got married and had children, some of whom had relationships with mortal men and women. In verse 4 we learn that the name of these half-breed children, Nephilim. The Nephilim were great warriors and legendary heros. Verse 5 says that people were getting pretty wicked, and the badness level was particularly high for a world of our size. Some have suggested that one of the signs of this depravity is the tale of the Nephilim; that the mixing of supernatural and human stocks was an affront to the natural order. In this story, however, there is no indication that the Nephilim were anything other than important and noble characters.
The world was getting it's wicked on, and that was something that irritated and angered God. Verse 6 tells us that God was sorry to have made humanity, "it grieved him to his heart." God resolves to wipe out humanity along with everything else. Then God remembered that he kinda liked Noah (who we'll talk more about later).
The Game:
In campaign settings like Forgotten Realms, the gods and goddesses are near-by, active in the world and meddlesome in the affairs of mortals. In addition to the recognized gods and goddesses there are a host of other spiritual beings (extra-planar creatures). Like in our text today, a world brimming with such creatures would inevitable spawn races of hybrids: in game terms, the elemental Genassi, the Aasimar and their lower planes brethren the Tifling.
I have been playing an Aasimar in a long ranging campaign in the Forgotten Realms setting, so I for the first time have been thinking about these races and how I would run them as a DM. The first consideration is, how weird are they: Planetouched characters are not all identical, like mutt puppies the various lineages show up differently in different individuals. ECL is your friend (and while it may not be the player's best friend it can be helpful to them too) use the ECL to determine how unexpected or odd the character should seem to the general populace. A character with and ECL of 1 will seem much more tame to NPCs than would an ECL 3 or 4 character. The second consideration is, how many are there: Is your party made up of planetouched, are there two or three, just one? The more planetouched you have in the party the more of an acceptance problem they're going to have, but it's a fabulous opportunity to move play off the prime. However if there is only one character, chances are that even if the evil wizard could spell her to some other plane, you're not going to want to run a single player adventure while everybody else gets bored and looses interest.
A third consideration on a more adventure writing note: maybe it does mess with the natural order of things. An interesting story line might involve PC's being asked by one god to keep other planar or spiritual beings from fiddling with a particular population and making more planetouched. Another story line might see the characters protecting infant or childling "Nephilim" from angry or regretful deities.