I'm currently designing a campaign world in which Nephilim a.k.a. Planetouched form a great portion of the populace, and "Monster" races using AU/AE racial class levels (as opposed to the WotC versions from Savage Species).
The Nephilim will essentially be a template that can be applied to any sentient being, and each subtype has characteristics based upon the extraplanar ancestor's origins. For example, the ones based on the Fey will have Drift, and so might those decended from beings from the Far Realms. Those with Elemental forebears would have certain elemental characteristics. In accord with the campaign design, instead of LA, the Nephilim template grants its abilities as PC-type levels.