Is there any way to buy extra sets of "legs" for the walker expansion sets so that all of the units in that expansion can be used? For instance, in the medium panzer expansion you only get the option of having Ludwig, Luther or Lothar - can more "legs" be purchased so that you can have all three?

There's no way to buy extra legs that I know of. However at $25 a piece you get one walker, assembled, primed, with multiple options and it's still 16% cheaper than some other companies unassembled walker kit.

With all due respect, I think you´re not getting it Davot.

Te walkers have the same body (and legs), and off course, only one of them comes in the box. But, since all models share main body and swap weapons, the box comes with ALL three equipment options ofr the arms.

So, YES! You already get the three options when you buy the box.

I fully understand the versatility of the walkers; you can interchange between the different types of walkers, as desired...but I want the whole box to be useable at the same time. In other words, just in case my post was unclear, I want to buy a box where all the walker designs in the box can be assembled at the same time, thus making a vast contribution to my army size. Sorry for the confusion.

You can't, you just buy them individually and make them up however you want.