We can make Humans have a little bit of elf or dwarf or even ogre in the family, but not the other way around.
That's a little difficult when the 'standard' human template is 'Medium Folk Walker with a base speed of 30 ft.' It's much easier to start with a human then add on the effects of the Blood feat.
Quite right. I spent a goodly deal puzzling over those feats, and starting with Human is the only thing that made sense - I do not see how a half-human/half-ogre is any different from a half-ogre/half-human, except that writing it that way creates another dozen feats or so
True enough. I didn't make any claims that it would be easy.
Probably a Human blooded feat would simply impart a degree of human versatility. So, a couple of options that the players would choose. Origin skill, maybe a bonus to a save of choice, a trick. That sort of thing.
Per RAW, you do not even need 'blood' an Unborn with Ogre Blooded??? Pech Blooded Rootwalker? sometimes the GM just has to saw "um... no."
Unlike D&D, Humans are no more versatile than other races except that they get Talents - both "base" species get the same number of skill points, origin skills, etc. - and I'm not about to start giving species Talents, especially when the species have Species feats. That way lies madness and game design purgatory.
And per the RAW, you DO need blood to take a Blood feat - all require Folk as a prereq