So, with both Allomancy and Feruchemy, there's 16 metals which each do 16 different things inclusive of the magic's idea. But Hermalurgy (that we know of) not only steals 'standard' effects, but also interacts with the other metal systems. Which leads me to conjecture that it was developed after the other two magics, or re-engineered.
Now let's say it wasn't remade. Which came first, All. or Fer.? I'd say Feruchemy, the 'shared' power....
Well of course, this was all though of before Eric came along and shot me down, *rolls eyes* lol, have it anyway.