Even if you could put the harness under the fot bed i wouldn't do it. I think that having a removable harness (and liners) not only satisfies those who do not want the harness, but the "removableness" i believe also serves as a better release mechanism on crashes, putting less stress on you AND on your boots and board. The liners are not as hard to put back in as some people say (just need a little practice to figure out the best way... i'm gona have to make a vid of this for the heck of it) I am actually starting to believe that whenever i DO get ejected from my boots it is a more "comfortable ejection" than others because the inner liner is cushioning the actions happening. the whole removable interior is just making more and more sense... to me.
ohh and here is the web site for the "Poron footbed " material which was also mentioned on the tag in the D2 box http://www.rogerscorporation.com/hpf/CT/Poron-F/Footwear%20homepage.htm