If you were to take the guts out of the iPhone 1, and replace them with iPhone 4s, it should work right? Given the parts are smaller, but all the buttons are in the same spot, and the screen is the same size. I don't want to do this, I just thought that It might be possible.
I'd imagine it would be tough to get everything to line up correctly. The internals of the 4S are much thinner than the original iPhone. So you'd have to secure everything in there so it doesn't bang around within the casing, and then on top of that, if the headphone jack and dock connector are were centered in the 4S and the original iPhone, the 4S ones wouldn't line up with the holes in the original casing if the screen was flush under the glass. Plus, the antenna in the 4S was much different than whatever was originally in the iPhone and it'd be tough to figure out how to make it work. It'd be an interesting project, but I don't think it'd be worth it. Too many changes and adaptations. There's a good chance it wouldn't work at all.
Possible... yes. Actually doable with the limits of human precision and patience... most likely not. Unless you're Ben Heck