I realize it's not really part of the theory, but the "things sticking together" part of Windrunning is the manipulation of atmospheric pressure.
Brandon has said that Hemalurgy is basically "stapling" someone else's spiritual DNA onto your own. So it's not really a genetic thing, though that has to do with what is there for Hemalurgy to steal.
That's very true, if you, say, put Preservation with Endowment, it would probably create something completely different from either of them. I'd love to see how the different powers match up. It offers quite a bit of fodder for just how Hoid's powers work.
It's also kind of my pet theory that the unaccounted for quarter of the metals in Hemalurgy (four each for Allomancy, Feruchemy and human attributes) could be for stealing other powers in outside magic systems. That would be so cool.