You could, but I wouldn't even bother. I posted this question on here long ago, and it became my mission to figure it out.
Basically you'd export the model in .obj format then load it into 3D Studio Max and reduce the polygons. The Poser models aren't made for real time use, they're made to look nice with trillions of polygons. The problem with reducing the number of polygons is that it destroys the model - the more you remove the worse it looks. The model's polygons cease to be symmetrical and jagged edges start sticking out. Good luck trying to fix it, it's like trying to build a box with wet spaghetti noodles.
Then, after you've reduced the polygons, you'll take this abomination unto the Lord with its 8000 polygons (that's about as far as you can reduce it before it explodes), and rig it to the skeleton of your choosing. The easiest way to get a rig if you don't have one is to load an animated model into Ultimate Unwrap 3D and save it as a Milkshape .ms3d file. Open the .ms3d file in Milkshape, delete the polygons but not the skeleton, and import the Poser model (you'll need to have converted it to a Milkshape format beforehand). Then you rig the vertices to the skeleton and you'll have a smoothly animated Frankenstein complete with holes in his face and jagged growths on his back.
Good luck.
Come see the WIP!