This may interesting some. I was looking at KeyShot again, and spotted a possibly rather easy workflow from Poser Pro to KeyShot, without .OBJ or .FBX files.
FAQ: Which 3D files can I import into KeyShot? [Last Updated – Jan 25, 2019]
* Cinema 4D R18 and prior (.c4d)
So, theoretically… Poser Pro scene > open Poser scene in Cinema 4D via Smith Micro’s PoserFusion plugin > save scene as .C4D > into KeyShot.
Speed of photoreal rendering, and access to the really cool sci-fi and weathering materials from KeyShot Cloud are the main reasons why you might want to do this. Though human skin rendering is probably going to be a bit ‘off’, compared to doing it in Poser. And hair and eyelash transparency-maps may not make it to KeyShot.