What if someone wrote a program that would let you rig a figure to work in Poser, Studio, 3DS Max, or Blender?

 

The closest you'll get to that is FBX import/export. It's part of Poser game dev and works decently. Last I heard Blender's FBX plug doesn't function too well and they didn't seem all that crazy about making it work, but that was a couple years back so maybe it's working better now. 

You'll never be able to get a figure that works seamlessly across platforms unless those platforms are all using the same rigging system, and that usually only happens when the same company is building both platforms, but even then, not always. 

And, Poser's rigging system is pretty outdated and cumbersome compared to everything else that's out there today, so we'll need to wait and see what SM does with it in the future. 

But for now we do have FBX (thanks Autodesk).